Dang it....you are right Greg.
names <- c("ABC", "ABCD", "ABCDE", "ABCDEF")
> substr(names, 1, nchar(names) - 1)
[1] "AB" "ABC" "ABCD" "ABCDE"
and...that is faster than using gsub().
Thanks for catching that....now it's time for cawfee....
Marc
On Apr 30, 2010, at 6:28 PM, Greg Snow wrote:
> 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.s...@imail.org
> 801.408.8111
>
>
>> -----Original Message-----
>> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-
>> project.org] On Behalf Of Marc Schwartz
>> Sent: Friday, April 30, 2010 5:04 PM
>> To: Sebastian Kruk
>> Cc: r-help@r-project.org; r-h...@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
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