R - How to use readline() with additional code after?

Question

Simple problem, but I can't find an answer that works anywhere. When I use readline() (for example, as demonstrated here - http://www.rexamples.com/4/Reading%20user%20input) it works perfectly:

readinteger <- function()
{ 
n <- readline(prompt="Enter an integer: ")
return(as.integer(n))
}
a <- print(readinteger())

However, if I add any code after this, readline() is skipped and the code just continues:

readinteger <- function()
{ 
n <- readline(prompt="Enter an integer: ")
return(as.integer(n))
}
a <- print(readinteger())
b <- 7

Any solutions (and/or easier ways to get user input)?

flodel · Accepted Answer · 2014-10-18 19:57:00Z

2

The problem here is that as soon as a <- print(readinteger()) is entered, it is evaluated, and b <- 7 is interpreted as the input to readline. A solution is to wrap your code in a function or a block:

{
a <- print(readinteger())
b <- 7
}

By putting everything into a block, the whole block is read as code and only after, as it is evaluated, you will be prompted for an integer.

edited Oct 18, 2014 at 19:57

answered Oct 18, 2014 at 19:51

flodel

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4 Comments

jdfinch3 Over a year ago

Thank you! I had played with brackets, thinking it was the answer - but apparently didn't get it right. One important thing I just figured out though - NOTHING can be after the last bracket. Not even blank lines or empty space. That's very important.

jdfinch3 Over a year ago

I seem to have run into a followup problem. Using this method, I can only get the lest line of code returned from the bracketed section. Example:

readinteger <- function()     {      n <- readline(prompt="Enter an integer: ")     return(as.integer(n))     }      {     a <- print(readinteger())     b <- a + 10     c <- 20       a     b     c     }

In that code, the only results displayed are a (the user input) and c (the last line of code)

flodel Over a year ago

You'll need to use print.

jdfinch3 Over a year ago

:facepalm: I didn't even think that one through. Thanks again!

RAguest · Accepted Answer · 2019-12-23 00:31:02Z

0

put multiple outputs if processed by your function or the print function into "ONE object"

you name it: myOput <- list(abandoned.b,that.c) print(myoutput)

answered Dec 23, 2019 at 0:31

RAguest

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