[R] Basic question: Reading in multiple choice question responses to a single column in data frame

[Magnus Torfason]

Are you looking for something like this?

 > d      = data.frame(a=1:5,b=c("1","2,3","2","3,4","1"))
 > d
   a   b
1 1   1
2 2 2,3
3 3   2
4 4 3,4
5 5   1
 > multis = strsplit(d$b,",")
 > counts = sapply(strsplit(d$b,","),length )
 > d2 = data.frame( a=rep(d$a,counts), b=unlist(multis) )
 > d2
   a b
1 1 1
2 2 2
3 2 3
4 3 2
5 4 3
6 4 4
7 5 1

Best,
Magnus


On 8/19/2009 3:12 PM, Damion Dooley wrote:
> I'm using read.delim to successfully read in tab delimited data, but some
> columns' values are comma seperated, reflecting the fact that user chose a
> few answers on a multi-select question.  I understand that each answer is
> its own category and so could be represented as a seperate column in the
> data set, but I'd like the option of reading in the data column, and
> converting it to a vector that has all row values (comma seperated or not)
> each have their own vector entry, so that the "table(columnData)" function
> does counts correctly.
>  
> So some code:
>  
>     myData = read.delim(myDataFile, row.names=1,header=TRUE,skip=10); #works
> fine
>     myColumn = myData[[question]]; #works fine, selects correct question
> column data
>  
> myColumn data is now e.g.:
>  
>     1
>     0
>     2
>     0,2
>     0
>     3
>     2
>     2,1
>  
> with the comma seperated values looking like atomic string values I guess.
> But I would like:
>  
>     1
>     0
>     2
>     0
>     2
>     0
>     3
>     2
>     2
>     1
>  
> I've tried various things, e.g. grep to recognize and expand the comma
> seperated values, but since vector functions are at work, I can only replace
> 1 value back into the myColumn data, e.g. "0,2" entry becomes "0" or "2" if
> I use 
>  
>     myColumn=gsub("^([0-9]+),([0-9]+),$",c('\\1'),myColumn,perl=TRUE) #or
> replace with c('\\2')
>  
> but I can't replace into c('\\1','\\2') 
>  
> Any elegant or otherwise ways to do this?
>  
> Much appreciated,
>  
> Damion
>  
>  
> 
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> 
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