R help - Apr 2003 - system() and R 1.7

I am using the system(command, input=a character vector) command on a
Windows NT machine and I now get the following warning with R 1.7:

Warning message: 
the condition has length > 1 and only the first element will be used in: if
(input != "") { 

I think I am getting this warning because, according to Peter Dalgaard, R
1.7 now gives a warning if if() and while() are called with a vector
condition.  Is there anyway to fix this issue besides options(warn=-1)?
Thanks.
> system
function (command, intern = FALSE, wait = TRUE, input = "",
show.output.on.console = FALSE, 
    minimized = FALSE, invisible = FALSE) 
{
    f <- ""
    if (input != "") {
        f <- tempfile()
        on.exit(unlink(f))
        cat(input, file = f, sep = "\n")
    }
    if (intern) 
        flag <- 3
    else {
        if (wait) 
            flag <- ifelse(show.output.on.console, 2, 1)
        else flag <- 0
    }
    if (invisible) 
        flag <- 20 + flag
    else if (minimized) 
        flag <- 10 + flag
    .Internal(system(command, as.integer(flag), f))
}
<environment: namespace:base>

Benjamin Stabler
Transportation Planning Analysis Unit
Oregon Department of Transportation
555 13th Street NE, Suite 2
Salem, OR 97301  Ph: 503-986-4104

Benjamin.STABLER at odot.state.or.us wrote:
> 
> I am using the system(command, input=a character vector) command on a
> Windows NT machine and I now get the following warning with R 1.7:
> 
> Warning message:
> the condition has length > 1 and only the first element will be used in:
if
> (input != "") {
> 
> I think I am getting this warning because, according to Peter Dalgaard, R
> 1.7 now gives a warning if if() and while() are called with a vector
> condition.  Is there anyway to fix this issue besides options(warn=-1)?
> Thanks.
The fix to system would be as follows (just those two lines):

> > system
> function (command, intern = FALSE, wait = TRUE, input = "",
 function (command, intern = FALSE, wait = TRUE, input = NULL,
> show.output.on.console = FALSE,
>     minimized = FALSE, invisible = FALSE)
> {
>     f <- ""
>     if (input != "") {
    if(!is.null(input)){
>         f <- tempfile()
>         on.exit(unlink(f))
>         cat(input, file = f, sep = "\n")
>     }
>     if (intern)
>         flag <- 3
>     else {
>         if (wait)
>             flag <- ifelse(show.output.on.console, 2, 1)
>         else flag <- 0
>     }
>     if (invisible)
>         flag <- 20 + flag
>     else if (minimized)
>         flag <- 10 + flag
>     .Internal(system(command, as.integer(flag), f))
> }
> <environment: namespace:base>
> 
> Benjamin Stabler
> Transportation Planning Analysis Unit
> Oregon Department of Transportation
> 555 13th Street NE, Suite 2
> Salem, OR 97301  Ph: 503-986-4104

Uwe Ligges

On Fri, 18 Apr 2003 11:04:48 -0700, you wrote:
>I am using the system(command, input=a character vector) command on a
>Windows NT machine and I now get the following warning with R 1.7:
>
>Warning message: 
>the condition has length > 1 and only the first element will be used in:
if
>(input != "") { 
>
This is a bug, fixed in the current patch version.  To fix your own,
you could edit the file library/base/R/base, as follows:

27878c27879
< system <- function(command, intern = FALSE, wait = TRUE, input =
"",
---
> system <- function(command, intern = FALSE, wait = TRUE, input = NULL,
27883c27884
<     if (input!="") {
---
>     if (!is.null(input)) {
The top lines are the released version, the lower lines are the patch.

Duncan Murdoch