corr.R

corr <- function(directory, threshold = 0) {
  ## 'directory' is a character vector of length 1 indicating
  ## the location of the CSV files
  
  ## 'threshold' is a numeric vector of length 1 indicating the
  ## number of completely observed observations (on all
  ## variables) required to compute the correlation between
  ## nitrate and sulfate; the default is 0
  
  ## Return a numeric vector of correlations
  
  total<-numeric()
  for(file in list.files(directory)){
    pollutantData<-read.table(paste(directory,"/",file,sep=""),sep=",",header=TRUE)
    comple<-nrow(pollutantData[complete.cases(pollutantData),])
    if(comple>threshold){
      #total<-rbind(total,cor(pollutantData$nitrate,pollutantData$sulfate,use="complete.obs"))
      total<-c(total,cor(pollutantData$nitrate,pollutantData$sulfate,use="complete.obs"))
    }
  }
  as.numeric(total)
}