Question

I’ve got a simple function script, the last line of which is to call the function

fun<-function(){
    readline("This is a test")
    x<-c(4,5)
    y<-c(5,6)
    add<-x+y
    sub<-x-y
    return(list(add,sub))
}

fun()

If I copy this into my R console I get what is to be expected

This is a test
[[1]]
[1]  9 11

[[2]]
[1] -1 -1

But I have been trying to use “source” to automatically pull up my scripts. If I try and use source

source("/Users/Me/Desktop/R.test.R")

I loose my output. I still get the readline, but I loose the return data so I just get this:

This is a test

I can still use source command to access my function if I delete the last line, and then manually type in “fun()”

source("/Users/Me/Desktop/R.test.R")
fun()

but I’d like to make this a one step deal.

Can someone explain why the difference between a “cut and paste” vs using source, and how I use source to call my functions in one step?

Thanks

Answer 1

When you type things directly in the console, R by default calls print on that object in order to display it. But it only does that directly in the console.

Try setting print.eval = TRUE when you call source. To see what’s going on, try it both ways with this script:

fun<-function(){
    readline("This is a test")
    x<-c(4,5)
    y<-c(5,6)
    add<-x+y
    sub<-x-y
    return(list(add,sub))
}

fun()

x <- 5
x

Now it’s a little more explicit. Just typing x at the console silently causes R to print it. If you want that behavior when sourcing, you have to say so.