Lesson 19: Text Editing and IDEs

In trying out our function zeroToNAs above, you probably used your computer’s mouse to copy-and-paste from this tutorial into your machine. Your screen would then look like this:

> zerosToNAs <- function(d,cols) 
+ {
+    zeroIndices <- which(d[,cols] == 0)
+    d[zeroIndices,cols] <- NA
+    d
+ }

But this is unwieldy. Typing it in line by line is laborious and error-prone. And what if we were to change the code? Must we type in the whole thing again? We really need a text editor for this. Just as we edit, say, reports, we do the same for code.

Here are your choices:

1. If you are already using an IDE, say RStudio, you simply edit in the designated pane.

2. If you are using an external editor, say vim or emacs, just open a new file and use that workspace.

3. For those not using these, we’ll just use R’s built-in edit function.

Option 3 is fine for now, but eventually you’ll want to use either Option 1 or 2. You may wish to start with one of those options now, before going further.

We have details on getting start with RStudio in the Appendix at the end of this document.

Consider the following toy example:

f <- function(x,y)
{
   s <- x + y
   d <- x - y
   c(s,d)
}

It finds the sum and difference of the inputs, and returns them as a two-element vector.

If you are using RStudio or an external editor, copy-and-paste the above code into the workspace of an empty file.

Or, to create f using edit, we would do the following:

> f <- edit()

This would invoke the text editor, which will depend on your machine. It will open your text editor right there in your R window. Type the function code, then save it, using the editor’s Save command.

IMPORTANT: Even if you are not using edit, it’s important to know what is happening in that command above.

a. edit itself is a function. Its return value is the code you typed in!

b. That code is then assigned to f, which you can now call

If you want to change the function, in the RStudio/external editor case, just edit it there. In the edit case, type

> f <- edit(f)

This again opens the text editor, but this time with the current f code showing. You edit the code as desired, then as before, the result is reassigned to f.

How do you then run the code, say for computing f(5,2)?

• If you had created f() using edit(), then execute as usual:

> f(5,2)

• If you had used an external text editor, say saving the code into the file a.R, then

> source('a.R')

loads file, and then you run as above.

• In RStudio, click on Source, then run as above.