[R] drop last character in a names'vector

[Greg Snow]

No, substr is vectorized, you just have a typo, you are using a different vector for nchar than you are subsetting.

-- 
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 Marc Schwartz
> Sent: Friday, April 30, 2010 5:04 PM
> To: Sebastian Kruk
> Cc: r-help at r-project.org; r-help at stat.math.ethz.ch
> Subject: Re: [R] drop last character in a names'vector
> 
> 
> On Apr 30, 2010, at 5:44 PM, Sebastian Kruk wrote:
> 
> > Hi, i have a vector filled with names:
> >
> > [1] Alvaro Adela ...
> > [25] Beatriz Berta ...
> > ...
> > [100000] ...
> >
> > I would like to drop last character in every name.
> >
> > I use the next program:
> >
> > for (i in 1:100000) {
> >                           largo <- nchar(names[i]-1)
> >                           names[i] <- substring (names[i],1,largo]
> >                          }
> >
> > Is another and faster way of do it?
> >
> > Thanks,
> >
> > Sebastián.
> 
> 
> As is the case with R, more than one, but the fastest may be:
> 
> names <- c("Alvaro Adela", "Beatriz Berta")
> 
> > gsub("^(.*).{1}$", "\\1", names)
> [1] "Alvaro Adel"  "Beatriz Bert"
> 
> 
> Just to show that it works with entries of varying lengths:
> 
> > gsub("^(.*).{1}$", "\\1", c("ABC", "ABCD", "ABCDE", "ABCDEF"))
> [1] "AB"    "ABC"   "ABCD"  "ABCDE"
> 
> 
> See ?gsub and ?regex
> 
> 
> 
> You could use substr(), but the arguments for substring lengths are not
> vectorized, so the following won't work:
> 
> > substr(c("ABC", "ABCD", "ABCDE", "ABCDEF"), 1, nchar(names) - 1)
> [1] "ABC"    "ABCD"   "ABCDE"  "ABCDEF"
> 
> 
> You would have to do something like this:
> 
> > as.vector(sapply(c("ABC", "ABCD", "ABCDE", "ABCDEF"),
>             function(x) substr(x, 1, nchar(x) - 1)))
> [1] "AB"    "ABC"   "ABCD"  "ABCDE"
> 
> 
> See ?substr and ?nchar
> 
> HTH,
> 
> Marc Schwartz
> 
> ______________________________________________
> 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.