R help - Feb 2003 - removing leading/trailing blanks

Hi,

What's the best way of dropping leading or trailing
blanks from a character string?  

The only thing I can think of is using sub() to replace
blanks with null strings, but I don't know if there is
a better way (I also don't know how to represent the
trailing blank in a regular expression).

Thanks,
Doug Grove

Douglas Grove wrote:
> Hi,
> 
> What's the best way of dropping leading or trailing
> blanks from a character string?  
> 
> The only thing I can think of is using sub() to replace
> blanks with null strings, but I don't know if there is
> a better way (I also don't know how to represent the
> trailing blank in a regular expression).
> 

I would use gsub instead:

R> ch = "    lkj df klj lkjsdf  "
R> ch
[1] "    lkj df klj lkjsdf  "
R> gsub("^ .", "", ch) # remove leading white space
[1] "lkj df klj lkjsdf  "
R> gsub(". $", "", ch) # remove trailing white space
[1] "    lkj df klj lkjsdf"
R>

Regards,
Sundar

> Hi,
>
> What's the best way of dropping leading or trailing
> blanks from a character string?
>
> The only thing I can think of is using sub() to replace
> blanks with null strings, but I don't know if there is
> a better way (I also don't know how to represent the
> trailing blank in a regular expression).
>
> Thanks,
> Doug Grove
sub ("^[ \t]*", "", sub ("[ \t]*$", "",
"  hello  "))

As an extension of the recent discussion of "functions different in R 
and S", what suggestions do people have for writing transportable code 
for R/S beyond Venables and Ripley (2000, S Programming, pp. 202-203)?

For example, I recently found myself using the following construct:

	if(version$major < 5){
#		Function oldClass was introduced with the "new S"
#		and is not present in R or S-Plus 2000
		oldClass <- class
	}

Similarly, I plan to define a function "gsub" 
if(is.null(version$language)).

Do these seem reasonable?  Are there other suggestions / standard / 
compilations of thoughts?

Thanks,
Spencer Graves