coping with a warning in if()

c('simple', 'complete') %in% c("simple", "s", "complete", "c")

Hi,

I'm sure this one is very easy....

I am trying to write a function where one of its arguments has two posible (strings) values,
defaulting to one of them if none is specified. My problem is that when evaluating the function
the following warning is produced:

"the condition has length > 1 and only the first element will be used"

I've read the help page of if() but I don't get it because when evaluating step by step the
warning is not produced.


Omitting the details of my function, below is an example of this

## Function
fun <- function( n, result = c("simple", "complete") )
{
?if ( is.null(result) )
? ? result <- ?"simple"
?if ( !(result %in% c("simple", "s", "complete", "c")) ) {
? ? ?stop("specify type of result 'simple' or 'complete'")
?} else {
?res <- rnorm(n)
?res
?}
}

## This gives the warning
fun(n=20)

## But this not
fun(n=20, result="other")

## The warning is not produced when doing this step by step
?n <- 20
?result <- ?"simple"
?if ( !(result %in% c("simple", "s", "complete", "c")) ){
? ? ?stop("specify type of result 'simple' or 'complete'")
?} else {
?res <- rnorm(n)
?res
?}

## or here
?n <- 20
?result <- ?"other"
?if ( !(result %in% c("simple", "s", "complete", "c")) ){
? ? ?stop("specify type of result 'simple' or 'complete'")
?} else {
?res <- rnorm(n)
?res
?}


Thanks for your time

H?ctor


--
H?ctor Villalobos <hvillalo at ipn.mx>
?CICIMAR - IPN
?A.P. 592. Col. Centro
?La Paz, Baja California Sur, M?XICO. 23000
?Tels. (+52 612) 122 53 44; 123 46 58; 123 47 34 ?ext. 82425
?Fax. ?(+52 612) 122 53 22

-----Original Message-----
From: r-help-bounces at r-project.org 
[mailto:r-help-bounces at r-project.org] On Behalf Of H?ctor Villalobos
Sent: Wednesday, 20 January 2010 10:34 a.m.
To: R-help at r-project.org
Subject: [R] coping with a warning in if()

Hi,

I'm sure this one is very easy....

I am trying to write a function where one of its arguments 
has two posible (strings) values, defaulting to one of them 
if none is specified. My problem is that when evaluating the 
function the following warning is produced:

"the condition has length > 1 and only the first element will be used"

I've read the help page of if() but I don't get it because 
when evaluating step by step the warning is not produced.


Omitting the details of my function, below is an example of this 

## Function
fun <- function( n, result = c("simple", "complete") )
{
  if ( is.null(result) ) 
     result <-  "simple" 
  if ( !(result %in% c("simple", "s", "complete", "c")) ) {
      stop("specify type of result 'simple' or 'complete'")
 } else {
  res <- rnorm(n)
  res
 }
}

## This gives the warning
fun(n=20)

## But this not
fun(n=20, result="other")

## The warning is not produced when doing this step by step
  n <- 20
  result <-  "simple" 
  if ( !(result %in% c("simple", "s", "complete", "c")) ){
      stop("specify type of result 'simple' or 'complete'")
 } else {
  res <- rnorm(n)
  res
 }

## or here
  n <- 20
  result <-  "other" 
  if ( !(result %in% c("simple", "s", "complete", "c")) ){
      stop("specify type of result 'simple' or 'complete'")
 } else {
  res <- rnorm(n)
  res
 }


Thanks for your time

H?ctor


-- 
H?ctor Villalobos <hvillalo at ipn.mx> 
 CICIMAR - IPN
 A.P. 592. Col. Centro 
 La Paz, Baja California Sur, M?XICO. 23000
 Tels. (+52 612) 122 53 44; 123 46 58; 123 47 34  ext. 82425
 Fax.  (+52 612) 122 53 22