Question

I have a very basic question on how to create a function and loop it in R.
Given my data with:

    #create a test df
    a<-c(1,2,3,4,5,6,7)
    b<-c(1,2,4,4,5,6,7)
    c<-c(1,7,1,7,2,5,4)
    d<-c(1,7,1,7,2,5,4)
    df.abcd<-data.frame(a,b,c,d)

I want to automatically create Boxplots and save their outputs. It works fine like this:

    # Create Boxplots from all columns
    for (x in 1:length(df.abcd)) {
      windows()#opens a graphics window - necesarry for the plots
      boxplot(df.abcd[,x], 
      main=names(df.abcd)[x])#writes colnames as title
      savePlot(filename=paste("E:\\R\\2_outputs\\boxplot_,deparse(x)), type="tiff")
      dev.off()#disables the graphics window
    }

Now I would like to make my procedure a function so that I can apply it on several Dataframes without repeating my code. I thought of someting like:

    #make the above a function and apply it
    test.function<-function(y){
      for (x in 1:length(y)){
      windows()
      boxplot(y[,x], 
      main=names(y)[x])
      savePlot(filename=paste("E:\\R\\2_outputs\\boxplot_,deparse(x)), type="tiff")
      dev.off()
    }}
    test.function(df.abcd)

So in the end this function works but it doesn’t loop any more. Only the first column of my dataframe is created as an output.
What am I doing wrong?

Answer 1

you have some mistakes in your code. (change x to y and add ” for the path name).
This should work:

test.function<-function(y){
  for (x in 1:length(y)){
    windows()
    boxplot(y[,x],   main=names(y)[x])
    savePlot(filename=paste("E:\\R\\2_outputs\\boxplot_",deparse(x)), type="tiff")
      dev.off()
    }
}

it is better to do something like this ( it the same as @Joris answer, maybe it is better to use tiff directly here)

test.function<-function(y){
  for (x in 1:length(y)){
    png(paste("E:\\R\\2_outputs\\boxplot_",deparse(x),'.tiff'))
    pp <- boxplot(y[,x],   main=names(y)[x])
    dev.off()
    }
}

test.function(df.abcd)