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Soeren.Vogel at eawag.ch

2009-Nov-22 11:26 UTC

[R] Define return values of a function

I have created a function to do something:

i <- factor(sample(c("A", "B", "C", NA), 793,
rep=T, prob=c(8, 7, 5,
1)))
k <- factor(sample(c("X", "Y", "Z", NA), 793,
rep=T, prob=c(12, 7, 9,
1)))
mytable <- function(x){
   xtb <- x
   btx <- x
   # do more with x, not relevant here
   cat("The table has been created, see here:\n")
   print(xtb)
   list(table=xtb, elbat=btx)
}
tbl <- table(i, k)
mytable(tbl) # (1)
z <- mytable(tbl) # (2)
str(z) # (3)

(1) Wanted: outputs the string and the table properly. *Unwanted*:  
outputs the list elements.

(2) and (3) Wanted: outputs the string properly. Wanted: assigns the  
list properly.

How can I get rid of the *unwanted* part? That is, how do I define  
what the functions prints and -- on the other hand -- what it returns  
without printing?

Thanks

S?ren

-- 
S?ren Vogel, Dipl.-Psych. (Univ.), PhD-Student, Eawag, Dept. SIAM
http://www.eawag.ch, http://sozmod.eawag.ch

baptiste auguie

2009-Nov-22 11:36 UTC

head link

[R] Define return values of a function

hi,

Try making your last line

 invisible( list(table=xtb, elbat=btx) )


HTH,

baptiste

2009/11/22 Soeren.Vogel <Soeren.Vogel at
eawag.ch>:> I have created a function to do something:
>
> i <- factor(sample(c("A", "B", "C", NA),
793, rep=T, prob=c(8, 7, 5, 1)))
> k <- factor(sample(c("X", "Y", "Z", NA),
793, rep=T, prob=c(12, 7, 9, 1)))
> mytable <- function(x){
> ?xtb <- x
> ?btx <- x
> ?# do more with x, not relevant here
> ?cat("The table has been created, see here:\n")
> ?print(xtb)
> ?list(table=xtb, elbat=btx)
> }
> tbl <- table(i, k)
> mytable(tbl) # (1)
> z <- mytable(tbl) # (2)
> str(z) # (3)
>
> (1) Wanted: outputs the string and the table properly. *Unwanted*: outputs
the list elements.
>
> (2) and (3) Wanted: outputs the string properly. Wanted: assigns the list
properly.
>
> How can I get rid of the *unwanted* part? That is, how do I define what the
functions prints and -- on the other hand -- what it returns without printing?
>
> Thanks
>
> S?ren
>
> --
> S?ren Vogel, Dipl.-Psych. (Univ.), PhD-Student, Eawag, Dept. SIAM
> http://www.eawag.ch, http://sozmod.eawag.ch
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

David Winsemius

2009-Nov-22 13:44 UTC

head link

[R] Define return values of a function

On Nov 22, 2009, at 6:26 AM, soeren.vogel at eawag.ch wrote:
> I have created a function to do something:
>
> i <- factor(sample(c("A", "B", "C", NA),
793, rep=T, prob=c(8, 7, 5,
> 1)))
> k <- factor(sample(c("X", "Y", "Z", NA),
793, rep=T, prob=c(12, 7,
> 9, 1)))
> mytable <- function(x){
>  xtb <- x
>  btx <- x
>  # do more with x, not relevant here
>  cat("The table has been created, see here:\n")
>  print(xtb)
>  list(table=xtb, elbat=btx)
> }
> tbl <- table(i, k)
> mytable(tbl) # (1)
> z <- mytable(tbl) # (2)
> str(z) # (3)
>
> (1) Wanted: outputs the string and the table properly. *Unwanted*:  
> outputs the list elements.
>
Whet the author of a function wants a particular object that exists  
insode a function to be returned they may warp it in the function  
return(). Otherwise R returns the result of the last evaluation which  
in this case was list(table=xtb, elbat=btx).

If you want the function to return <something else>. then you could   
put <something else> last in the sequence. If you want it to return  
<nothing> than put this at the end:

return()

If you want the results to not be printed the use invisible()

Perhaps:
  invisible(list( elbat=btx))   #substituted for list(table=xtb,  
elbat=btx) after the print line

 > tbl <- table(i, k)
 > mytable(tbl) # (1)
The table has been created, see here:
    k
i     X   Y   Z
   A 119  69  89
   B 116  70  97
   C  80  36  52
 > z <- mytable(tbl) # (2)
The table has been created, see here:
    k
i     X   Y   Z
   A 119  69  89
   B 116  70  97
   C  80  36  52
 > str(z) # (3)
List of 1
  $ elbat: 'table' int [1:3, 1:3] 119 116 80 69 70 36 89 97 52
   ..- attr(*, "dimnames")=List of 2
   .. ..$ i: chr [1:3] "A" "B" "C"
   .. ..$ k: chr [1:3] "X" "Y" "Z"


> (2) and (3) Wanted: outputs the string properly. Wanted: assigns the  
> list properly.
If you want to return the list, elbat, then just put the name of the  
list last in your case inside invisible or put it inside return().

>
> How can I get rid of the *unwanted* part? That is, how do I define  
> what the functions prints
That set by cat and print in your case.
> and -- on the other hand -- what it returns without printing?
By return()  or the order of evaluation>
--

David Winsemius, MD
Heritage Laboratories
West Hartford, CT

Greg Snow

2009-Nov-23 17:31 UTC

head link

[R] Define return values of a function

If you want to control what gets printed in the output of your function, then
you need to get into creating classes and methods.  Choose a class to return
from your function, and create a print method for that class, then when you run
your function the output will cause the print method to be called if you
don't store the object, but the entire object will be available if stored. 
E.g.:

testfunc <- function(x) {
	out <- list( a=summary(x), b=quantile(x), c=range(x) )
	class(out) <- 'myclass'
	return(out)
}

print.myclass <- function(x) {
	cat('my output:\n')
	print(x$a)
	cat('\n\n')
	cat('Q1: ',x$b[2], '\n')
	return(invisible(x))
}

testfunc(rnorm(100))
tmp <- testfunc(rnorm(100))
tmp
str(tmp)

Hope this helps,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Soeren.Vogel at eawag.ch
> Sent: Sunday, November 22, 2009 4:27 AM
> To: r-help at r-project.org
> Subject: [R] Define return values of a function
> 
> I have created a function to do something:
> 
> i <- factor(sample(c("A", "B", "C", NA),
793, rep=T, prob=c(8, 7, 5,
> 1)))
> k <- factor(sample(c("X", "Y", "Z", NA),
793, rep=T, prob=c(12, 7, 9,
> 1)))
> mytable <- function(x){
>    xtb <- x
>    btx <- x
>    # do more with x, not relevant here
>    cat("The table has been created, see here:\n")
>    print(xtb)
>    list(table=xtb, elbat=btx)
> }
> tbl <- table(i, k)
> mytable(tbl) # (1)
> z <- mytable(tbl) # (2)
> str(z) # (3)
> 
> (1) Wanted: outputs the string and the table properly. *Unwanted*:
> outputs the list elements.
> 
> (2) and (3) Wanted: outputs the string properly. Wanted: assigns the
> list properly.
> 
> How can I get rid of the *unwanted* part? That is, how do I define
> what the functions prints and -- on the other hand -- what it returns
> without printing?
> 
> Thanks
> 
> S?ren
> 
> --
> S?ren Vogel, Dipl.-Psych. (Univ.), PhD-Student, Eawag, Dept. SIAM
> http://www.eawag.ch, http://sozmod.eawag.ch
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

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