Try this:
DF <- data.frame(A = c('11_12', '22_23', '33_34'),
B = sample(3))
#1) Using strsplit
transform(DF, C = sapply(strsplit(as.character(DF$A), "_"), '[', 1))
#2) Using substr
transform(DF, C = substr(DF$A, 1, 2))
#3) Using regex
transform(DF, C = gsub("_.*", "", DF$A))
On Fri, Sep 25, 2009 at 11:01 AM, Dry, Jonathan R
<jonathan....@astrazeneca.com> wrote:
> Currently as the first column in a data frame I have string values in the
> format xx_yy - I want to create a new column with just the substring xx (for
> each row in turn). Three possible ways to do this might be (1) split the
> string by '_' using strsplit and paste the first of the resulting variables
> into a new column, but I have been unable to do this for each row of my data
> frame in turn (trying to use apply); (2) split the column into two based on
> '_', but I am not sure if this is possible; (3) use a regular expression to
> return the substring up to the '_', but I am unsure how to make a regular
> expression return the substring it matches to in R.
>
> Any ideas on all three counts would be gratefully recieved.
>
> --------------------------------------------------------------------------
> AstraZeneca UK Limited is a company incorporated in Engl...{{dropped:21}}
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O
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