[R] case conversion and/or string comparison

Kaspar Pflugshaupt pflugshaupt at geobot.umnw.ethz.ch
Fri Nov 16 13:45:00 CET 2001

On 16.11.2001 12:37 Uhr, Randall Skelton wrote:

> This is no doubt trivial but after searching the help files and the web, I
> cannot seem to find it.
> 1) How do I convert 'hgt' into 'HGT' in R?

There are the functions tolower() and toupper(). They work as one would

> toupper("hgt")
[1] "HGT"

With either of them, the comparison you mention is easy:

compareCaseless <- function(string1, string2)
    return(toupper(string1) == toupper(string2))

> compareCaseless("hgt", "HGT")
[1] TRUE

> 2) How should I have used the help facilities to find this?

Hmm. help.search("case") does not give them, nor does help.search("string").
Nor do, in fact, help.search("upper") or "lower". I just found them
indirectly via help.search("character"), which mentioned the chartr()
function. On its help page, those two functions are noted.

Maybe they deserve to be better advertised?


Kapar Pflugshaupt 


Kaspar Pflugshaupt
Geobotanisches Institut
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