R help - Jan 2011 - dataframe: string operations on columns

Dear all,
how can I perform a string operation like strsplit(x," ")  on a column
of a dataframe, and put the first or the second item of the split into a 
new dataframe column?
(so that on each row it is consistent)

Thanks
Boris

Hi,

I guess it's not the nicest way to do it, but it should work for you:

#create some sample data
df <- data.frame(a=c("A B", "C D", "A C",
"A D", "B D"),
stringsAsFactors=FALSE)
#split the column by space
df_split <- strsplit(df$a, split=" ")

#place the first element into column a1 and the second into a2
for (i in 1:length(df_split[[1]])){
  df[i+1] <- unlist(lapply(df_split, FUN=function(x) x[i]))
  names(df)[i+1] <- paste("a",i,sep="")
}

I hope people will give you more compact solutions.
HTH,
Ivan



Le 1/18/2011 16:30, boris pezzatti a ?crit :
>
> Dear all,
> how can I perform a string operation like strsplit(x," ")  on a
column
> of a dataframe, and put the first or the second item of the split into 
> a new dataframe column?
> (so that on each row it is consistent)
>
> Thanks
> Boris
>
> ______________________________________________
> R-help at r-project.org mailing list
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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.
>
-- 
Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
Abt. S?ugetiere
Martin-Luther-King-Platz 3
D-20146 Hamburg, GERMANY
+49(0)40 42838 6231
ivan.calandra at uni-hamburg.de

**********
http://www.for771.uni-bonn.de
http://webapp5.rrz.uni-hamburg.de/mammals/eng/1525_8_1.php

> how can I perform a string operation like strsplit(x," ") ?on a
column of a
> dataframe, and put the first or the second item of the split into a new
> dataframe column?
> (so that on each row it is consistent)
Have a look at str_split_fixed in the stringr package.

Hadley


-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/