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<!DOCTYPE html>
<html >
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>R User Notebook</title>
<meta name="description" content="A notebook of useful R code and concepts">
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<meta name="twitter:title" content="R User Notebook" />
<meta name="twitter:description" content="A notebook of useful R code and concepts" />
<meta name="author" content="Kieran Driscoll">
<meta name="date" content="2019-02-11">
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<ul class="summary">
<li class="chapter" data-level="1" data-path="index.html"><a href="index.html"><i class="fa fa-check"></i><b>1</b> R User Notebook</a></li>
<li class="chapter" data-level="2" data-path="basic-concepts.html"><a href="basic-concepts.html"><i class="fa fa-check"></i><b>2</b> Basic Concepts</a><ul>
<li class="chapter" data-level="2.1" data-path="basic-concepts.html"><a href="basic-concepts.html#vectors"><i class="fa fa-check"></i><b>2.1</b> Vectors</a></li>
<li class="chapter" data-level="2.2" data-path="basic-concepts.html"><a href="basic-concepts.html#matrices"><i class="fa fa-check"></i><b>2.2</b> Matrices</a></li>
<li class="chapter" data-level="2.3" data-path="basic-concepts.html"><a href="basic-concepts.html#dataframes"><i class="fa fa-check"></i><b>2.3</b> Dataframes</a></li>
<li class="chapter" data-level="2.4" data-path="basic-concepts.html"><a href="basic-concepts.html#tibbles"><i class="fa fa-check"></i><b>2.4</b> Tibbles</a></li>
<li class="chapter" data-level="2.5" data-path="basic-concepts.html"><a href="basic-concepts.html#extracting-data-from-dataframestibbles"><i class="fa fa-check"></i><b>2.5</b> Extracting data from Dataframes/Tibbles</a></li>
<li class="chapter" data-level="2.6" data-path="basic-concepts.html"><a href="basic-concepts.html#lists"><i class="fa fa-check"></i><b>2.6</b> Lists</a></li>
<li class="chapter" data-level="2.7" data-path="basic-concepts.html"><a href="basic-concepts.html#factors"><i class="fa fa-check"></i><b>2.7</b> Factors</a></li>
<li class="chapter" data-level="2.8" data-path="basic-concepts.html"><a href="basic-concepts.html#dates"><i class="fa fa-check"></i><b>2.8</b> Dates</a></li>
<li class="chapter" data-level="2.9" data-path="basic-concepts.html"><a href="basic-concepts.html#style-guide"><i class="fa fa-check"></i><b>2.9</b> Style Guide</a></li>
</ul></li>
<li class="chapter" data-level="3" data-path="importing-exporting.html"><a href="importing-exporting.html"><i class="fa fa-check"></i><b>3</b> Importing & Exporting</a><ul>
<li class="chapter" data-level="3.1" data-path="importing-exporting.html"><a href="importing-exporting.html#importing-with-base-r"><i class="fa fa-check"></i><b>3.1</b> Importing with Base R</a></li>
<li class="chapter" data-level="3.2" data-path="importing-exporting.html"><a href="importing-exporting.html#importing-with-other-packages"><i class="fa fa-check"></i><b>3.2</b> Importing with other packages</a><ul>
<li class="chapter" data-level="3.2.1" data-path="importing-exporting.html"><a href="importing-exporting.html#importing-a-csv"><i class="fa fa-check"></i><b>3.2.1</b> Importing a CSV</a></li>
<li class="chapter" data-level="3.2.2" data-path="importing-exporting.html"><a href="importing-exporting.html#importing-a-tsv"><i class="fa fa-check"></i><b>3.2.2</b> Importing a TSV</a></li>
<li class="chapter" data-level="3.2.3" data-path="importing-exporting.html"><a href="importing-exporting.html#importing-a-r-data-file"><i class="fa fa-check"></i><b>3.2.3</b> Importing a R data file</a></li>
<li class="chapter" data-level="3.2.4" data-path="importing-exporting.html"><a href="importing-exporting.html#importing-a-excel-file"><i class="fa fa-check"></i><b>3.2.4</b> Importing a Excel file</a></li>
<li class="chapter" data-level="3.2.5" data-path="importing-exporting.html"><a href="importing-exporting.html#importing-a-sas-file"><i class="fa fa-check"></i><b>3.2.5</b> Importing a SAS file</a></li>
<li class="chapter" data-level="3.2.6" data-path="importing-exporting.html"><a href="importing-exporting.html#importing-json-newline-delimited-json"><i class="fa fa-check"></i><b>3.2.6</b> Importing JSON (Newline Delimited JSON)</a></li>
</ul></li>
<li class="chapter" data-level="3.3" data-path="importing-exporting.html"><a href="importing-exporting.html#exporting"><i class="fa fa-check"></i><b>3.3</b> Exporting</a><ul>
<li class="chapter" data-level="3.3.1" data-path="importing-exporting.html"><a href="importing-exporting.html#write-to-an-r-dataset"><i class="fa fa-check"></i><b>3.3.1</b> Write to an R dataset</a></li>
<li class="chapter" data-level="3.3.2" data-path="importing-exporting.html"><a href="importing-exporting.html#write-to-an-csv-file"><i class="fa fa-check"></i><b>3.3.2</b> Write to an CSV file</a></li>
</ul></li>
</ul></li>
<li class="chapter" data-level="4" data-path="manipulating-data.html"><a href="manipulating-data.html"><i class="fa fa-check"></i><b>4</b> Manipulating data</a><ul>
<li class="chapter" data-level="4.1" data-path="manipulating-data.html"><a href="manipulating-data.html#basic-data-wrangling"><i class="fa fa-check"></i><b>4.1</b> Basic data wrangling</a></li>
<li class="chapter" data-level="4.2" data-path="manipulating-data.html"><a href="manipulating-data.html#summary-statistics"><i class="fa fa-check"></i><b>4.2</b> Summary statistics</a></li>
<li class="chapter" data-level="4.3" data-path="manipulating-data.html"><a href="manipulating-data.html#conditional-statements"><i class="fa fa-check"></i><b>4.3</b> Conditional statements</a></li>
<li class="chapter" data-level="4.4" data-path="manipulating-data.html"><a href="manipulating-data.html#recode"><i class="fa fa-check"></i><b>4.4</b> Recode</a></li>
<li class="chapter" data-level="4.5" data-path="manipulating-data.html"><a href="manipulating-data.html#appending-columns-and-rows"><i class="fa fa-check"></i><b>4.5</b> Appending columns and rows</a></li>
<li class="chapter" data-level="4.6" data-path="manipulating-data.html"><a href="manipulating-data.html#joins"><i class="fa fa-check"></i><b>4.6</b> Joins</a></li>
<li class="chapter" data-level="4.7" data-path="manipulating-data.html"><a href="manipulating-data.html#tidy-data"><i class="fa fa-check"></i><b>4.7</b> Tidy Data</a></li>
<li class="chapter" data-level="4.8" data-path="manipulating-data.html"><a href="manipulating-data.html#tibbles-1"><i class="fa fa-check"></i><b>4.8</b> tibbles</a></li>
</ul></li>
<li class="chapter" data-level="5" data-path="functions.html"><a href="functions.html"><i class="fa fa-check"></i><b>5</b> Functions</a><ul>
<li class="chapter" data-level="5.1" data-path="functions.html"><a href="functions.html#function-basics---an-example-using-str"><i class="fa fa-check"></i><b>5.1</b> Function Basics - an example using str()</a></li>
<li class="chapter" data-level="5.2" data-path="functions.html"><a href="functions.html#common-base-functions"><i class="fa fa-check"></i><b>5.2</b> Common (base) functions</a><ul>
<li class="chapter" data-level="5.2.1" data-path="functions.html"><a href="functions.html#strings"><i class="fa fa-check"></i><b>5.2.1</b> Strings</a></li>
<li class="chapter" data-level="5.2.2" data-path="functions.html"><a href="functions.html#mathematical"><i class="fa fa-check"></i><b>5.2.2</b> Mathematical</a></li>
<li class="chapter" data-level="5.2.3" data-path="functions.html"><a href="functions.html#properties-lookups"><i class="fa fa-check"></i><b>5.2.3</b> Properties & Lookups</a></li>
<li class="chapter" data-level="5.2.4" data-path="functions.html"><a href="functions.html#transformation"><i class="fa fa-check"></i><b>5.2.4</b> Transformation</a></li>
<li class="chapter" data-level="5.2.5" data-path="functions.html"><a href="functions.html#other-useful-functions"><i class="fa fa-check"></i><b>5.2.5</b> Other useful functions</a></li>
</ul></li>
<li class="chapter" data-level="5.3" data-path="functions.html"><a href="functions.html#stringr---more-string-functions"><i class="fa fa-check"></i><b>5.3</b> Stringr - more string functions</a></li>
<li class="chapter" data-level="5.4" data-path="functions.html"><a href="functions.html#lubridate---more-date-functions"><i class="fa fa-check"></i><b>5.4</b> Lubridate - more date functions</a></li>
<li class="chapter" data-level="5.5" data-path="functions.html"><a href="functions.html#converting-data-to-other-formats"><i class="fa fa-check"></i><b>5.5</b> Converting data to other formats</a><ul>
<li class="chapter" data-level="5.5.1" data-path="functions.html"><a href="functions.html#json"><i class="fa fa-check"></i><b>5.5.1</b> JSON</a></li>
</ul></li>
<li class="chapter" data-level="5.6" data-path="functions.html"><a href="functions.html#user-defined-functions"><i class="fa fa-check"></i><b>5.6</b> User Defined Functions</a></li>
<li class="chapter" data-level="5.7" data-path="functions.html"><a href="functions.html#chainingpiping"><i class="fa fa-check"></i><b>5.7</b> Chaining/Piping</a></li>
</ul></li>
<li class="chapter" data-level="6" data-path="loops.html"><a href="loops.html"><i class="fa fa-check"></i><b>6</b> Loops</a><ul>
<li class="chapter" data-level="6.1" data-path="loops.html"><a href="loops.html#basic-for-loop-structure"><i class="fa fa-check"></i><b>6.1</b> Basic for Loop structure</a></li>
<li class="chapter" data-level="6.2" data-path="loops.html"><a href="loops.html#looping-through-a-vector"><i class="fa fa-check"></i><b>6.2</b> Looping through a vector</a></li>
<li class="chapter" data-level="6.3" data-path="loops.html"><a href="loops.html#creating-a-list-in-a-loop"><i class="fa fa-check"></i><b>6.3</b> Creating a List in a Loop</a></li>
<li class="chapter" data-level="6.4" data-path="loops.html"><a href="loops.html#looping-with-apply-functions"><i class="fa fa-check"></i><b>6.4</b> Looping with apply functions</a></li>
</ul></li>
<li class="chapter" data-level="7" data-path="tables.html"><a href="tables.html"><i class="fa fa-check"></i><b>7</b> Tables</a><ul>
<li class="chapter" data-level="7.1" data-path="tables.html"><a href="tables.html#displaying-tables---htmltable"><i class="fa fa-check"></i><b>7.1</b> Displaying tables - htmlTable</a></li>
<li class="chapter" data-level="7.2" data-path="tables.html"><a href="tables.html#displaying-interactive-tables---dt"><i class="fa fa-check"></i><b>7.2</b> Displaying Interactive tables - DT</a></li>
<li class="chapter" data-level="7.3" data-path="tables.html"><a href="tables.html#creating-tabulations"><i class="fa fa-check"></i><b>7.3</b> Creating Tabulations</a></li>
</ul></li>
<li class="chapter" data-level="8" data-path="charts.html"><a href="charts.html"><i class="fa fa-check"></i><b>8</b> Charts</a><ul>
<li class="chapter" data-level="8.0.1" data-path="charts.html"><a href="charts.html#static-charts-with-ggplot2"><i class="fa fa-check"></i><b>8.0.1</b> Static charts with ggplot2</a></li>
<li class="chapter" data-level="8.0.2" data-path="charts.html"><a href="charts.html#changing-axes"><i class="fa fa-check"></i><b>8.0.2</b> Changing Axes</a></li>
<li class="chapter" data-level="8.0.3" data-path="charts.html"><a href="charts.html#chart-themes-styles"><i class="fa fa-check"></i><b>8.0.3</b> Chart Themes & Styles</a></li>
<li class="chapter" data-level="8.0.4" data-path="charts.html"><a href="charts.html#line-charts-geom_line"><i class="fa fa-check"></i><b>8.0.4</b> Line Charts (geom_line)</a></li>
<li class="chapter" data-level="8.0.5" data-path="charts.html"><a href="charts.html#bar-charts-geom_bar-geom_histogram"><i class="fa fa-check"></i><b>8.0.5</b> Bar Charts (geom_bar & geom_histogram)</a></li>
<li class="chapter" data-level="8.0.6" data-path="charts.html"><a href="charts.html#adding-features"><i class="fa fa-check"></i><b>8.0.6</b> Adding features</a></li>
<li class="chapter" data-level="8.0.7" data-path="charts.html"><a href="charts.html#heatmaps"><i class="fa fa-check"></i><b>8.0.7</b> Heatmaps</a></li>
<li class="chapter" data-level="8.0.8" data-path="charts.html"><a href="charts.html#boxplots"><i class="fa fa-check"></i><b>8.0.8</b> Boxplots</a></li>
<li class="chapter" data-level="8.0.9" data-path="charts.html"><a href="charts.html#combination-charts"><i class="fa fa-check"></i><b>8.0.9</b> Combination Charts</a></li>
<li class="chapter" data-level="8.0.10" data-path="charts.html"><a href="charts.html#scales"><i class="fa fa-check"></i><b>8.0.10</b> Scales</a></li>
<li class="chapter" data-level="8.0.11" data-path="charts.html"><a href="charts.html#ggplot-wizard"><i class="fa fa-check"></i><b>8.0.11</b> ggplot wizard</a></li>
<li class="chapter" data-level="8.0.12" data-path="charts.html"><a href="charts.html#interactive-charts-with-ggiraph"><i class="fa fa-check"></i><b>8.0.12</b> Interactive charts with ggiraph</a></li>
<li class="chapter" data-level="8.0.13" data-path="charts.html"><a href="charts.html#interactive-charts-with-dygraph"><i class="fa fa-check"></i><b>8.0.13</b> Interactive charts with dygraph</a></li>
</ul></li>
<li class="chapter" data-level="9" data-path="maps.html"><a href="maps.html"><i class="fa fa-check"></i><b>9</b> Maps</a><ul>
<li class="chapter" data-level="9.1" data-path="maps.html"><a href="maps.html#leaflet"><i class="fa fa-check"></i><b>9.1</b> Leaflet</a><ul>
<li class="chapter" data-level="9.1.1" data-path="maps.html"><a href="maps.html#display-a-basic-map"><i class="fa fa-check"></i><b>9.1.1</b> Display a basic map</a></li>
<li class="chapter" data-level="9.1.2" data-path="maps.html"><a href="maps.html#add-markers-shapes-and-popups-to-a-map"><i class="fa fa-check"></i><b>9.1.2</b> Add markers, shapes and popups to a map</a></li>
<li class="chapter" data-level="9.1.3" data-path="maps.html"><a href="maps.html#add-boundaries"><i class="fa fa-check"></i><b>9.1.3</b> Add Boundaries</a></li>
<li class="chapter" data-level="9.1.4" data-path="maps.html"><a href="maps.html#add-interactivity"><i class="fa fa-check"></i><b>9.1.4</b> Add Interactivity</a></li>
<li class="chapter" data-level="9.1.5" data-path="maps.html"><a href="maps.html#attach-extra-information-to-your-boundary-dataset"><i class="fa fa-check"></i><b>9.1.5</b> Attach extra information to your boundary dataset</a></li>
<li class="chapter" data-level="9.1.6" data-path="maps.html"><a href="maps.html#add-colour-based-on-area-data"><i class="fa fa-check"></i><b>9.1.6</b> Add colour based on area data</a></li>
</ul></li>
<li class="chapter" data-level="9.2" data-path="maps.html"><a href="maps.html#inserting-html-javascript-directly-into-r"><i class="fa fa-check"></i><b>9.2</b> Inserting HTML & Javascript directly into R</a></li>
</ul></li>
<li class="chapter" data-level="10" data-path="rmarkdown-knitr.html"><a href="rmarkdown-knitr.html"><i class="fa fa-check"></i><b>10</b> RMarkdown & Knitr</a><ul>
<li class="chapter" data-level="10.1" data-path="rmarkdown-knitr.html"><a href="rmarkdown-knitr.html#knitr"><i class="fa fa-check"></i><b>10.1</b> Knitr</a></li>
<li class="chapter" data-level="10.2" data-path="rmarkdown-knitr.html"><a href="rmarkdown-knitr.html#yaml"><i class="fa fa-check"></i><b>10.2</b> YAML</a></li>
<li class="chapter" data-level="10.3" data-path="rmarkdown-knitr.html"><a href="rmarkdown-knitr.html#modular-coding"><i class="fa fa-check"></i><b>10.3</b> Modular coding</a></li>
</ul></li>
<li class="chapter" data-level="11" data-path="machine-learning-predictive-analytics.html"><a href="machine-learning-predictive-analytics.html"><i class="fa fa-check"></i><b>11</b> Machine Learning & Predictive Analytics</a><ul>
<li class="chapter" data-level="11.0.1" data-path="machine-learning-predictive-analytics.html"><a href="machine-learning-predictive-analytics.html#decision-trees"><i class="fa fa-check"></i><b>11.0.1</b> Decision Trees</a></li>
</ul></li>
<li class="chapter" data-level="12" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html"><i class="fa fa-check"></i><b>12</b> Text Mining & NLP</a><ul>
<li class="chapter" data-level="12.0.1" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#text-data"><i class="fa fa-check"></i><b>12.0.1</b> Text data</a></li>
<li class="chapter" data-level="12.0.2" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#tidy-text"><i class="fa fa-check"></i><b>12.0.2</b> Tidy text</a></li>
<li class="chapter" data-level="12.0.3" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#stemming"><i class="fa fa-check"></i><b>12.0.3</b> Stemming</a></li>
<li class="chapter" data-level="12.0.4" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#basic-text-stats"><i class="fa fa-check"></i><b>12.0.4</b> Basic text stats</a></li>
<li class="chapter" data-level="12.0.5" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#n-grams-analysis"><i class="fa fa-check"></i><b>12.0.5</b> N-Grams analysis</a></li>
<li class="chapter" data-level="12.0.6" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#text-preparation-with-tm"><i class="fa fa-check"></i><b>12.0.6</b> Text Preparation with <strong>tm</strong></a></li>
<li class="chapter" data-level="12.1" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#create-a-term-document-matrix"><i class="fa fa-check"></i><b>12.1</b> Create a Term Document Matrix</a><ul>
<li class="chapter" data-level="12.1.1" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#from-a-corpus-by-default-words-are-converted-to-lowercase-less-than-3-characters-are-excluded"><i class="fa fa-check"></i><b>12.1.1</b> From a Corpus (by default words are converted to lowercase less than 3 characters are excluded)</a></li>
<li class="chapter" data-level="12.1.2" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#matrix-managment"><i class="fa fa-check"></i><b>12.1.2</b> Matrix Managment</a></li>
</ul></li>
<li class="chapter" data-level="12.2" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#topic-modelling-latent-dirichlet-allocation-lda"><i class="fa fa-check"></i><b>12.2</b> Topic Modelling & Latent Dirichlet Allocation (LDA)</a></li>
<li class="chapter" data-level="12.3" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#clustering---similarity-between-topics"><i class="fa fa-check"></i><b>12.3</b> Clustering - Similarity between topics</a></li>
<li class="chapter" data-level="12.4" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#calculating-distance-between-objects"><i class="fa fa-check"></i><b>12.4</b> Calculating distance between objects</a></li>
<li class="chapter" data-level="12.5" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#non-euclidian-distances---jensen-shannon"><i class="fa fa-check"></i><b>12.5</b> Non-Euclidian Distances - Jensen Shannon</a></li>
<li class="chapter" data-level="12.6" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#scaling---principal-components"><i class="fa fa-check"></i><b>12.6</b> Scaling - Principal Components</a></li>
<li class="chapter" data-level="12.7" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#eigen-vectors"><i class="fa fa-check"></i><b>12.7</b> Eigen vectors</a></li>
<li class="chapter" data-level="12.8" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#k-means"><i class="fa fa-check"></i><b>12.8</b> K-Means</a></li>
<li class="chapter" data-level="12.9" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#naive-bayes-classifiers"><i class="fa fa-check"></i><b>12.9</b> Naive Bayes Classifiers</a></li>
<li class="chapter" data-level="12.10" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#tf-idf-classifiers-supervised"><i class="fa fa-check"></i><b>12.10</b> TF-IDF Classifiers (Supervised)</a></li>
<li class="chapter" data-level="12.11" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#sentiment-analysis"><i class="fa fa-check"></i><b>12.11</b> Sentiment Analysis</a></li>
<li class="chapter" data-level="12.12" data-path="text-mining-nlp.html"><a href="text-mining-nlp.html#word-bubble"><i class="fa fa-check"></i><b>12.12</b> Word Bubble</a></li>
</ul></li>
<li class="chapter" data-level="13" data-path="shiny.html"><a href="shiny.html"><i class="fa fa-check"></i><b>13</b> Shiny</a><ul>
<li class="chapter" data-level="13.1" data-path="shiny.html"><a href="shiny.html#basic-shiny-structure"><i class="fa fa-check"></i><b>13.1</b> Basic Shiny Structure</a></li>
<li class="chapter" data-level="13.2" data-path="shiny.html"><a href="shiny.html#user-interface"><i class="fa fa-check"></i><b>13.2</b> User Interface</a><ul>
<li class="chapter" data-level="13.2.1" data-path="shiny.html"><a href="shiny.html#layout"><i class="fa fa-check"></i><b>13.2.1</b> Layout</a></li>
<li class="chapter" data-level="13.2.2" data-path="shiny.html"><a href="shiny.html#inputs"><i class="fa fa-check"></i><b>13.2.2</b> Inputs</a></li>
<li class="chapter" data-level="13.2.3" data-path="shiny.html"><a href="shiny.html#outputs"><i class="fa fa-check"></i><b>13.2.3</b> Outputs</a></li>
</ul></li>
<li class="chapter" data-level="13.3" data-path="shiny.html"><a href="shiny.html#server"><i class="fa fa-check"></i><b>13.3</b> Server</a><ul>
<li class="chapter" data-level="13.3.1" data-path="shiny.html"><a href="shiny.html#linking-to-ui-outputs"><i class="fa fa-check"></i><b>13.3.1</b> Linking to UI outputs</a></li>
<li class="chapter" data-level="13.3.2" data-path="shiny.html"><a href="shiny.html#linking-to-ui-inputs"><i class="fa fa-check"></i><b>13.3.2</b> Linking to UI inputs</a></li>
</ul></li>
<li class="chapter" data-level="13.4" data-path="shiny.html"><a href="shiny.html#shiny-dashboard"><i class="fa fa-check"></i><b>13.4</b> Shiny Dashboard</a></li>
</ul></li>
<li class="chapter" data-level="14" data-path="bookdown.html"><a href="bookdown.html"><i class="fa fa-check"></i><b>14</b> Bookdown</a><ul>
<li class="chapter" data-level="14.1" data-path="bookdown.html"><a href="bookdown.html#set-up"><i class="fa fa-check"></i><b>14.1</b> Set-up</a></li>
<li class="chapter" data-level="14.2" data-path="bookdown.html"><a href="bookdown.html#create-the-book"><i class="fa fa-check"></i><b>14.2</b> Create the book</a></li>
</ul></li>
<li class="chapter" data-level="15" data-path="creating-packages.html"><a href="creating-packages.html"><i class="fa fa-check"></i><b>15</b> Creating Packages</a><ul>
<li class="chapter" data-level="15.1" data-path="creating-packages.html"><a href="creating-packages.html#setup-folders"><i class="fa fa-check"></i><b>15.1</b> Setup Folders</a></li>
<li class="chapter" data-level="15.2" data-path="creating-packages.html"><a href="creating-packages.html#r-folder"><i class="fa fa-check"></i><b>15.2</b> R folder</a></li>
<li class="chapter" data-level="15.3" data-path="creating-packages.html"><a href="creating-packages.html#man-folder"><i class="fa fa-check"></i><b>15.3</b> man folder</a></li>
<li class="chapter" data-level="15.4" data-path="creating-packages.html"><a href="creating-packages.html#package-details"><i class="fa fa-check"></i><b>15.4</b> Package details</a></li>
<li class="chapter" data-level="15.5" data-path="creating-packages.html"><a href="creating-packages.html#package-dependencies"><i class="fa fa-check"></i><b>15.5</b> Package Dependencies</a></li>
<li class="chapter" data-level="15.6" data-path="creating-packages.html"><a href="creating-packages.html#build-the-package"><i class="fa fa-check"></i><b>15.6</b> Build the package</a></li>
<li class="chapter" data-level="15.7" data-path="creating-packages.html"><a href="creating-packages.html#making-changes"><i class="fa fa-check"></i><b>15.7</b> Making changes</a></li>
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<li class="chapter" data-level="16" data-path="git-version-control.html"><a href="git-version-control.html"><i class="fa fa-check"></i><b>16</b> Git - Version Control</a><ul>
<li class="chapter" data-level="16.1" data-path="git-version-control.html"><a href="git-version-control.html#set-up-1"><i class="fa fa-check"></i><b>16.1</b> Set-up</a></li>
<li class="chapter" data-level="16.2" data-path="git-version-control.html"><a href="git-version-control.html#link-git-to-a-github-account"><i class="fa fa-check"></i><b>16.2</b> Link Git to a GitHub account</a></li>
<li class="chapter" data-level="16.3" data-path="git-version-control.html"><a href="git-version-control.html#starting-a-project-with-github"><i class="fa fa-check"></i><b>16.3</b> Starting a project with Github</a></li>
<li class="chapter" data-level="16.4" data-path="git-version-control.html"><a href="git-version-control.html#hosting-a-site-on-github"><i class="fa fa-check"></i><b>16.4</b> Hosting a site on Github</a></li>
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<li class="chapter" data-level="17" data-path="other-languages.html"><a href="other-languages.html"><i class="fa fa-check"></i><b>17</b> Other Languages</a><ul>
<li class="chapter" data-level="17.1" data-path="other-languages.html"><a href="other-languages.html#sql"><i class="fa fa-check"></i><b>17.1</b> SQL</a></li>
<li class="chapter" data-level="17.2" data-path="other-languages.html"><a href="other-languages.html#python"><i class="fa fa-check"></i><b>17.2</b> Python</a></li>
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<section class="normal" id="section-">
<div id="functions" class="section level1">
<h1><span class="header-section-number">5</span> Functions</h1>
<div id="function-basics---an-example-using-str" class="section level2">
<h2><span class="header-section-number">5.1</span> Function Basics - an example using str()</h2>
<p>Functions are the main way that you will handle or manipulate data. Something is a function if it is in the form <strong>functionname(arg1, arg2, …)</strong></p>
<div class="sourceCode" id="cb53"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb53-1" data-line-number="1"><span class="kw">str</span>(mtcars) <span class="co">#Displays basic info about the data (like Proc Contents)</span></a></code></pre></div>
<p>To see what a function does, and what arguments it requires, you can enter the function name into the <strong>help</strong> function, eg help(str)</p>
</div>
<div id="common-base-functions" class="section level2">
<h2><span class="header-section-number">5.2</span> Common (base) functions</h2>
<div id="strings" class="section level3">
<h3><span class="header-section-number">5.2.1</span> Strings</h3>
<div class="sourceCode" id="cb54"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb54-1" data-line-number="1">x <-<span class="st"> "The cat sat on the mat"</span></a>
<a class="sourceLine" id="cb54-2" data-line-number="2"></a>
<a class="sourceLine" id="cb54-3" data-line-number="3"><span class="co"># Substring - Use with any vector or list. You should include the start and end position.</span></a>
<a class="sourceLine" id="cb54-4" data-line-number="4"><span class="kw">substr</span>(x, <span class="dv">3</span>, <span class="dv">4</span>) </a>
<a class="sourceLine" id="cb54-5" data-line-number="5"></a>
<a class="sourceLine" id="cb54-6" data-line-number="6"><span class="co"># Search for a string within a string - will return either TRUE or FALSE.</span></a>
<a class="sourceLine" id="cb54-7" data-line-number="7"><span class="kw">grepl</span>(<span class="st">"cat"</span>, x)</a>
<a class="sourceLine" id="cb54-8" data-line-number="8"></a>
<a class="sourceLine" id="cb54-9" data-line-number="9"><span class="co"># Find and replace a string within a string.</span></a>
<a class="sourceLine" id="cb54-10" data-line-number="10"><span class="kw">gsub</span>(<span class="st">"cat"</span>,<span class="st">"dog"</span>, x)</a>
<a class="sourceLine" id="cb54-11" data-line-number="11"></a>
<a class="sourceLine" id="cb54-12" data-line-number="12"><span class="co"># Paste - Concatenates vectors or lists (including an optional separator). All values will be converted into strings.</span></a>
<a class="sourceLine" id="cb54-13" data-line-number="13"><span class="kw">paste</span>(<span class="st">"value1"</span>, <span class="st">"value2"</span>, <span class="dt">sep=</span><span class="st">" "</span>)</a>
<a class="sourceLine" id="cb54-14" data-line-number="14"><span class="kw">paste0</span>(<span class="st">"value1"</span>, <span class="st">"value2"</span>) <span class="co"># This function doesnt have any separator</span></a>
<a class="sourceLine" id="cb54-15" data-line-number="15"></a>
<a class="sourceLine" id="cb54-16" data-line-number="16"><span class="co"># Remove leading/trailing whitespace from character strings with trimws() </span></a>
<a class="sourceLine" id="cb54-17" data-line-number="17"><span class="kw">trimws</span>(<span class="st">" Hello World "</span>) </a>
<a class="sourceLine" id="cb54-18" data-line-number="18"></a>
<a class="sourceLine" id="cb54-19" data-line-number="19"><span class="co"># Apply a special format to a number/string and return it as a string</span></a>
<a class="sourceLine" id="cb54-20" data-line-number="20"><span class="kw">sprintf</span>(<span class="st">'%03d'</span>, <span class="dv">1</span>) </a>
<a class="sourceLine" id="cb54-21" data-line-number="21"><span class="co">#This simple example converts 1 into a string and pads it with 0's so that it 3 characters long. The first argument defines what and how text willl be displayed. The % symbol is a placeholders that can have different types. All subsequent arguments represent the data variables that are represented by the placeholders (in the order they occur).For more info see https://www.rdocumentation.org/packages/base/versions/3.4.3/topics/sprintf.</span></a></code></pre></div>
</div>
<div id="mathematical" class="section level3">
<h3><span class="header-section-number">5.2.2</span> Mathematical</h3>
<p>Round/Floor/Ceiling</p>
<div class="sourceCode" id="cb55"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb55-1" data-line-number="1"><span class="kw">round</span>(<span class="fl">5.15</span>, <span class="dt">digits=</span><span class="dv">1</span>) <span class="co"># Specify number of decimal places to round to</span></a>
<a class="sourceLine" id="cb55-2" data-line-number="2"><span class="kw">round</span>(<span class="dv">515</span>, <span class="dt">digits=</span><span class="op">-</span><span class="dv">1</span>) <span class="co"># A negative digit rounds to the nearest 10^n (ie. 10, 100, 1000) </span></a>
<a class="sourceLine" id="cb55-3" data-line-number="3"><span class="kw">floor</span>(<span class="fl">5.15</span>) <span class="co"># Rounds down to nearest whole number</span></a>
<a class="sourceLine" id="cb55-4" data-line-number="4"><span class="kw">ceiling</span>(<span class="fl">5.15</span>) <span class="co"># Rounds up to nearest whole number</span></a></code></pre></div>
<p>Sum</p>
<div class="sourceCode" id="cb56"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb56-1" data-line-number="1"><span class="kw">sum</span>(<span class="kw">c</span>(<span class="dv">1</span>,<span class="dv">2</span>,<span class="dv">3</span>))</a>
<a class="sourceLine" id="cb56-2" data-line-number="2"><span class="kw">sum</span>(<span class="dv">1</span>,<span class="dv">2</span>,<span class="dv">4</span>)</a>
<a class="sourceLine" id="cb56-3" data-line-number="3"><span class="kw">sum</span>(mtcars<span class="op">$</span>wt)</a></code></pre></div>
</div>
<div id="properties-lookups" class="section level3">
<h3><span class="header-section-number">5.2.3</span> Properties & Lookups</h3>
<div class="sourceCode" id="cb57"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb57-1" data-line-number="1">x <-<span class="st"> </span><span class="kw">c</span>(<span class="dv">14</span>, <span class="ot">NA</span>, <span class="dv">35</span>, <span class="dv">64</span>)</a></code></pre></div>
<p>Length - The number of elements in an object</p>
<div class="sourceCode" id="cb58"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb58-1" data-line-number="1"><span class="kw">length</span>(<span class="st">"ABCDE"</span>) <span class="co"># A single vector has length 1</span></a></code></pre></div>
<pre><code>## [1] 1</code></pre>
<div class="sourceCode" id="cb60"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb60-1" data-line-number="1"><span class="kw">length</span>(x) <span class="co"># This concatenated vector has length 4</span></a></code></pre></div>
<pre><code>## [1] 4</code></pre>
<div class="sourceCode" id="cb62"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb62-1" data-line-number="1"><span class="kw">length</span>(mtcars) <span class="co"># The length of a Dataframe is equal to the number of columns</span></a></code></pre></div>
<pre><code>## [1] 11</code></pre>
<p>Logic functions for different types of value</p>
<div class="sourceCode" id="cb64"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb64-1" data-line-number="1"><span class="kw">is.na</span>(x) <span class="co"># Produces a vector Will be TRUE if a value is missing (ie. NA) </span></a></code></pre></div>
<pre><code>## [1] FALSE TRUE FALSE FALSE</code></pre>
<div class="sourceCode" id="cb66"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb66-1" data-line-number="1"><span class="kw">is.numeric</span>(x) <span class="co"># Will be TRUE if all values are numeric (ignores NA's) </span></a></code></pre></div>
<pre><code>## [1] TRUE</code></pre>
<p>Find the POSITION of the element with highest/lowest value</p>
<div class="sourceCode" id="cb68"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb68-1" data-line-number="1"><span class="kw">which.min</span>(x) </a>
<a class="sourceLine" id="cb68-2" data-line-number="2"><span class="kw">which.max</span>(x) </a></code></pre></div>
</div>
<div id="transformation" class="section level3">
<h3><span class="header-section-number">5.2.4</span> Transformation</h3>
<div class="sourceCode" id="cb69"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb69-1" data-line-number="1">x <-<span class="st"> </span><span class="kw">c</span>(<span class="dv">1000</span>, <span class="dv">1500</span>, <span class="dv">20000</span>)</a></code></pre></div>
<p>Reverse elements in a vector</p>
<div class="sourceCode" id="cb70"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb70-1" data-line-number="1"><span class="kw">rev</span>(x) </a></code></pre></div>
<p>Format numbers to include comma separators - this converts numbers to characters</p>
<div class="sourceCode" id="cb71"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb71-1" data-line-number="1"><span class="kw">format</span>(x, <span class="dt">big.mark=</span><span class="st">","</span>, <span class="dt">big.interval=</span>3L, <span class="dt">trim=</span><span class="ot">TRUE</span>)</a></code></pre></div>
<pre><code>## [1] "1,000" "1,500" "20,000"</code></pre>
<p>When a DataFrame/tibble has been created, various functions can be used to describe it, such as:</p>
<ul>
<li>dim() # Shows number of rows and colums</li>
<li>length() # Number of columns</li>
<li>colnames() # The column names</li>
<li>head() # Displays first 6 rows</li>
<li>str() # variable name, type and example values</li>
</ul>
<p>There are also some mathematical functions, including:
* summary() # Summary statistics for numeric columns (mean, min, max, Q1, Q3)
* colSums() # Sum of each column
* colMeans() # Mean of each column</p>
</div>
<div id="other-useful-functions" class="section level3">
<h3><span class="header-section-number">5.2.5</span> Other useful functions</h3>
<p>Generate a number sequence</p>
<div class="sourceCode" id="cb73"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb73-1" data-line-number="1"><span class="kw">seq</span>(<span class="dv">1</span>, <span class="dv">5</span>)</a></code></pre></div>
<pre><code>## [1] 1 2 3 4 5</code></pre>
<div class="sourceCode" id="cb75"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb75-1" data-line-number="1"><span class="kw">seq</span>(<span class="dv">1</span>, <span class="dv">5</span>, <span class="dt">by =</span> <span class="dv">2</span>)</a></code></pre></div>
<pre><code>## [1] 1 3 5</code></pre>
</div>
</div>
<div id="stringr---more-string-functions" class="section level2">
<h2><span class="header-section-number">5.3</span> Stringr - more string functions</h2>
<p>Loading packages will give you access to more complex functions:</p>
<div class="sourceCode" id="cb77"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb77-1" data-line-number="1"><span class="kw">library</span>(stringr)</a>
<a class="sourceLine" id="cb77-2" data-line-number="2">x <-<span class="st"> "string to test"</span></a>
<a class="sourceLine" id="cb77-3" data-line-number="3"></a>
<a class="sourceLine" id="cb77-4" data-line-number="4"><span class="co"># Count of words in a string</span></a>
<a class="sourceLine" id="cb77-5" data-line-number="5">stringr<span class="op">::</span><span class="kw">str_count</span>(x, <span class="st">" "</span>) <span class="co"># Different delimiters can be used</span></a></code></pre></div>
<pre><code>## [1] 2</code></pre>
<div class="sourceCode" id="cb79"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb79-1" data-line-number="1"><span class="co"># Substring</span></a>
<a class="sourceLine" id="cb79-2" data-line-number="2">stringr<span class="op">::</span><span class="kw">str_sub</span>(x, <span class="dv">1</span>, <span class="dv">6</span>)</a></code></pre></div>
<pre><code>## [1] "string"</code></pre>
<div class="sourceCode" id="cb81"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb81-1" data-line-number="1"><span class="co"># Split a string into N pieces base on your chosen delimiter - stored in a matrix</span></a>
<a class="sourceLine" id="cb81-2" data-line-number="2">stringr<span class="op">::</span><span class="kw">str_split_fixed</span>(x, <span class="st">"to"</span>, <span class="dv">2</span>) </a></code></pre></div>
<pre><code>## [,1] [,2]
## [1,] "string " " test"</code></pre>
<div class="sourceCode" id="cb83"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb83-1" data-line-number="1"><span class="co"># Find and replace a string within a string</span></a>
<a class="sourceLine" id="cb83-2" data-line-number="2">stringr<span class="op">::</span><span class="kw">str_replace_all</span>(x, <span class="st">"test"</span>, <span class="st">"replace"</span>)</a></code></pre></div>
<pre><code>## [1] "string to replace"</code></pre>
<div class="sourceCode" id="cb85"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb85-1" data-line-number="1"><span class="co"># Locate the start and end position of a string - stored in a matrix </span></a>
<a class="sourceLine" id="cb85-2" data-line-number="2">stringr<span class="op">::</span><span class="kw">str_locate</span>(x, <span class="st">"test"</span>)[[<span class="dv">1</span>]] <span class="co"># [[1]] is needed to return start, [[2]] to get end</span></a></code></pre></div>
<pre><code>## [1] 11</code></pre>
<div class="sourceCode" id="cb87"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb87-1" data-line-number="1"><span class="co"># Detect if a sub-string appears within a string </span></a>
<a class="sourceLine" id="cb87-2" data-line-number="2">stringr<span class="op">::</span><span class="kw">str_detect</span>(x, <span class="st">"test"</span>) <span class="co"># Returns either TRUE or FALSE</span></a></code></pre></div>
<pre><code>## [1] TRUE</code></pre>
<p>You can add regular expressions to these functions. <a href="https://stringr.tidyverse.org/articles/regular-expressions.html" class="uri">https://stringr.tidyverse.org/articles/regular-expressions.html</a></p>
</div>
<div id="lubridate---more-date-functions" class="section level2">
<h2><span class="header-section-number">5.4</span> Lubridate - more date functions</h2>
<p><strong>Lubridate</strong> helps parse, convert, and extract information from dates.</p>
<div class="sourceCode" id="cb89"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb89-1" data-line-number="1">date <-<span class="st"> "2017-04-06"</span></a>
<a class="sourceLine" id="cb89-2" data-line-number="2"></a>
<a class="sourceLine" id="cb89-3" data-line-number="3">lubridate<span class="op">::</span><span class="kw">day</span>(date)</a></code></pre></div>
<pre><code>## [1] 6</code></pre>
<div class="sourceCode" id="cb91"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb91-1" data-line-number="1">lubridate<span class="op">::</span><span class="kw">week</span>(date)</a></code></pre></div>
<pre><code>## [1] 14</code></pre>
<div class="sourceCode" id="cb93"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb93-1" data-line-number="1">lubridate<span class="op">::</span><span class="kw">month</span>(date,</a>
<a class="sourceLine" id="cb93-2" data-line-number="2"> <span class="dt">label =</span> <span class="ot">TRUE</span>, <span class="co"># Switch between numeric (FALSE) and character (TRUE) month.</span></a>
<a class="sourceLine" id="cb93-3" data-line-number="3"> <span class="dt">abbr =</span> <span class="ot">FALSE</span>) <span class="co"># Switch between full (FALSE) and abbreviated (TRUE) names. </span></a></code></pre></div>
<pre><code>## [1] April
## 12 Levels: January < February < March < April < May < June < ... < December</code></pre>
<div class="sourceCode" id="cb95"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb95-1" data-line-number="1">lubridate<span class="op">::</span><span class="kw">quarter</span>(date)</a></code></pre></div>
<pre><code>## [1] 2</code></pre>
<div class="sourceCode" id="cb97"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb97-1" data-line-number="1">lubridate<span class="op">::</span><span class="kw">year</span>(date)</a></code></pre></div>
<pre><code>## [1] 2017</code></pre>
</div>
<div id="converting-data-to-other-formats" class="section level2">
<h2><span class="header-section-number">5.5</span> Converting data to other formats</h2>
<div id="json" class="section level3">
<h3><span class="header-section-number">5.5.1</span> JSON</h3>
<p>The <strong>RJSONIO</strong> package can convert R objects into JSON.<br />
A vector/list will become a JSON array ["“,”“,”"]</p>
<div class="sourceCode" id="cb99"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb99-1" data-line-number="1">x <-<span class="st"> </span><span class="kw">c</span>(<span class="dv">1</span>,<span class="dv">2</span>,<span class="dv">4</span>,<span class="dv">8</span>,<span class="dv">16</span>)</a>
<a class="sourceLine" id="cb99-2" data-line-number="2">RJSONIO<span class="op">::</span><span class="kw">toJSON</span>(x) </a></code></pre></div>
<pre><code>## [1] "[ 1, 2, 4, 8, 16 ]"</code></pre>
<p>A dataframe or List will become a JSON object eg. {"“:[],”":[]}</p>
<div class="sourceCode" id="cb101"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb101-1" data-line-number="1">RJSONIO<span class="op">::</span><span class="kw">toJSON</span>(mtcars) </a></code></pre></div>
</div>
</div>
<div id="user-defined-functions" class="section level2">
<h2><span class="header-section-number">5.6</span> User Defined Functions</h2>
<p>The basic syntax to create a UDF is:</p>
<div class="sourceCode" id="cb102"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb102-1" data-line-number="1">myfunction <-<span class="st"> </span><span class="cf">function</span>(arg1, arg2, ... ){</a>
<a class="sourceLine" id="cb102-2" data-line-number="2"> statements</a>
<a class="sourceLine" id="cb102-3" data-line-number="3"><span class="kw">return</span>(object)</a>
<a class="sourceLine" id="cb102-4" data-line-number="4">}</a>
<a class="sourceLine" id="cb102-5" data-line-number="5"></a>
<a class="sourceLine" id="cb102-6" data-line-number="6"><span class="co">#For example this function checks whether a number is equal to 1 and returns a Yes/No vector:</span></a>
<a class="sourceLine" id="cb102-7" data-line-number="7">checkifone <-<span class="st"> </span><span class="cf">function</span>(x){</a>
<a class="sourceLine" id="cb102-8" data-line-number="8"> <span class="cf">if</span> (x<span class="op">==</span><span class="dv">1</span>) { <span class="kw">return</span>(<span class="st">"Yes"</span>) }</a>
<a class="sourceLine" id="cb102-9" data-line-number="9"> <span class="cf">else</span> <span class="kw">return</span>(<span class="st">"No"</span>)</a>
<a class="sourceLine" id="cb102-10" data-line-number="10">}</a>
<a class="sourceLine" id="cb102-11" data-line-number="11"></a>
<a class="sourceLine" id="cb102-12" data-line-number="12"><span class="co">#You can return any object, including vectors, list, other objects or functions.</span></a></code></pre></div>
<p>To use a function :</p>
<div class="sourceCode" id="cb103"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb103-1" data-line-number="1"><span class="kw">checkifone</span>(<span class="dv">23</span>)</a>
<a class="sourceLine" id="cb103-2" data-line-number="2"></a>
<a class="sourceLine" id="cb103-3" data-line-number="3"><span class="co"># Or save the result of the function in a new variable</span></a>
<a class="sourceLine" id="cb103-4" data-line-number="4">functionresult <-<span class="st"> </span><span class="kw">checkifone</span>(<span class="dv">23</span>) <span class="co">#functionresult will contain either Yes or NO ##</span></a></code></pre></div>
<p>Using dplyr in a function - Passing columns names to a function conating dplyr will not work:</p>
<div class="sourceCode" id="cb104"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb104-1" data-line-number="1">udf <-<span class="st"> </span><span class="cf">function</span>(d, x, y) {</a>
<a class="sourceLine" id="cb104-2" data-line-number="2"> </a>
<a class="sourceLine" id="cb104-3" data-line-number="3"> <span class="co"># Column names referenced in a function call must be converted with the enqou() function.</span></a>
<a class="sourceLine" id="cb104-4" data-line-number="4"> x <-<span class="st"> </span><span class="kw">enquo</span>(x)</a>
<a class="sourceLine" id="cb104-5" data-line-number="5"> y <-<span class="st"> </span><span class="kw">enquo</span>(y)</a>
<a class="sourceLine" id="cb104-6" data-line-number="6"> </a>
<a class="sourceLine" id="cb104-7" data-line-number="7"> <span class="co"># Columns names can now be used by adding the !! prefix (or use the UQ() function) </span></a>
<a class="sourceLine" id="cb104-8" data-line-number="8"> <span class="kw">return</span>(d <span class="op">%>%</span><span class="st"> </span><span class="kw">group_by</span>(<span class="op">!!</span>x) <span class="op">%>%</span><span class="st"> </span><span class="kw">summarise</span>(<span class="dt">n =</span><span class="kw">n</span>(), <span class="dt">avg=</span><span class="kw">mean</span>(<span class="op">!!</span>y)))</a>
<a class="sourceLine" id="cb104-9" data-line-number="9"> </a>
<a class="sourceLine" id="cb104-10" data-line-number="10">}</a>
<a class="sourceLine" id="cb104-11" data-line-number="11"><span class="kw">udf</span>(mtcars, cyl, mpg)</a></code></pre></div>
</div>
<div id="chainingpiping" class="section level2">
<h2><span class="header-section-number">5.7</span> Chaining/Piping</h2>
<p>There is an alternative way of writing R code that may be easier to read/understand. It is called chaining/piping, and it reduces the need for nested functions by using a special operator <strong>%>%</strong>.</p>
<div class="sourceCode" id="cb105"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb105-1" data-line-number="1"><span class="co">#Normal R code</span></a>
<a class="sourceLine" id="cb105-2" data-line-number="2">xvar <-<span class="st"> </span><span class="kw">c</span>(<span class="dv">1</span>,<span class="dv">1</span>,<span class="dv">2</span>,<span class="dv">3</span>,<span class="dv">5</span>,<span class="dv">8</span>,<span class="dv">13</span>,<span class="dv">21</span>) <span class="co">#initialses an array </span></a>
<a class="sourceLine" id="cb105-3" data-line-number="3">xresult <-<span class="st"> </span><span class="kw">round</span>(<span class="kw">log</span>(xvar),<span class="dv">1</span>) <span class="co"># Calculates the log, and rounds to nearest dp</span></a>
<a class="sourceLine" id="cb105-4" data-line-number="4"></a>
<a class="sourceLine" id="cb105-5" data-line-number="5"><span class="co">#Chaining/Piping</span></a>
<a class="sourceLine" id="cb105-6" data-line-number="6">xvar <-<span class="st"> </span><span class="kw">c</span>(<span class="dv">1</span>,<span class="dv">1</span>,<span class="dv">2</span>,<span class="dv">3</span>,<span class="dv">5</span>,<span class="dv">8</span>,<span class="dv">13</span>,<span class="dv">21</span>)</a>
<a class="sourceLine" id="cb105-7" data-line-number="7">xresult <-<span class="st"> </span>xvar <span class="op">%>%</span><span class="st"> </span><span class="kw">log</span>() <span class="op">%>%</span><span class="st"> </span><span class="kw">round</span>(<span class="dv">1</span>) </a>
<a class="sourceLine" id="cb105-8" data-line-number="8"><span class="co"># The %>% effectively passes xvar to the log() function and the result is passed to round(). This means that complex code with multiple functions should be easier to read</span></a></code></pre></div>
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