hw4-conditionals-testing.Rmd

---
title: "Homework 4 - Conditionals & Testing"
output:
  html_document:
    toc: false
    number_sections: false
params:
  number: 4
  submit: "https://u.pcloud.com/#page=puplink&code=5VYkZffcAIs7IEbYpIHvaob9Ab5Q4TAvy"
  purpose: |
    The purposes of this assignment are:
    >
    > - To practice using conditional statements while writing functions in R.
    > - To practice the skill of writing and using test functions to understand the problem.
    > - To practice computational problem solving.
---

```{r child = file.path("child", "setup.Rmd")}
```

```{r child = file.path("child", "hw.Rmd")}
```

> ### Using the [autograder](autograder.html)
>
> - You can check your solutions to problems 2 - 7 by logging into the [autograder](autograder.html) and uploading your `hw4.R` file.
> - **The file must be named `hw4.R` or it won't work.**
> - Your user name is your netID, and your password is inside the `readme.txt` file in the Box folder I shared with you.

### 1) Staying organized [SOLO, 5%]

Download and use [this template](templates/hw4.zip) for your assignment. Inside the "hw4" folder, open and edit the R script called "hw4.R" and fill out your name, Net ID, and the names of anyone you worked with on this assignment.

> ### **Writing test functions**
>
> For each of the following functions, write a test function first, and then write the function. **Your test functions will count for half of the available credit for each problem**. Think carefully about the test cases to include in your test functions.

### 2) `guessAnimal(hasFourLegs, climbsTrees)` [SOLO, 10%]

Write the function `guessAnimal(hasFourLegs, climbsTrees)` that returns a statement guessing an animal based on whether it has four legs and whether it climbs trees. Here is the expected behavior:

<div style="width:500px">
`hasFourLegs` | `climbsTrees` | statement
--------------|---------------|-------------
`TRUE`  | `TRUE`  | "It's probably a cat"
`TRUE`  | `FALSE` | "It's probably a dog"
`FALSE` | `TRUE`  | "It's probably a snake"
`FALSE` | `FALSE` | "Hmm, I'm not sure"
</div>

### 3) `isPositiveMultipleOf4Or7(n)` [SOLO, 15%]

Write the function `isPositiveMultipleOf4Or7(n)` that returns `TRUE` if `n` is a positive multiple of 4 or 7 and `FALSE` otherwise. Note than `n` could be any data type.

### 4) `isEvenPositiveInt(x)` [COLLABORATIVE, 20%]

Given an arbitrary value `x`, return `TRUE` if it is an integer, and it is positive, and it is even (all 3 must be true), or `FALSE` otherwise. If the value `x` is not an integer, the function should return `FALSE` rather than error. So, `isEvenPositiveInt("yikes!")` returns `FALSE`, and `isEvenPositiveInt(123456)` returns `TRUE`.

### 5) `isLeapYear(year)` [SOLO, 20%]

Write the function `isLeapYear(year)` that returns `TRUE` if `year` is a [leap year](https://www.mathsisfun.com/leap-years.html) and `FALSE` otherwise. Assume that `year` is a positive integer.

### 6) `getTheCents(n)` [COLLABORATIVE, 20%]

Write the function `getTheCents(n)` which takes a value `n` that represents a payment in US dollars and returns the number of cents in the payment. For example, if `n` is `2.45`, the function should return `45`. If `n` is an integer, the function should return `0`, as it has `0` cents; if it isn't a number, it should return `NULL`, because a non-number payment make no cents (ha!). If the payment has partial cents (for example, `3.953`), it should be rounded to the nearest cent (in this case, `95` cents).

### 7) Read and reflect [SOLO, 10%]

Read and reflect on next week's readings on [iteration](r5-iteration.html). Afterwards, in a comment (`#`) in your R file, write a short reflection on what you've learned and any questions or points of confusion you have about what we've covered thus far. This can just few a few sentences related to this assignment, next week's readings, things going on in the world that remind you something from class, etc. If there's anything that jumped out at you, write it down.