[R] Recoding lists of categories of a variable

[Jim Lemon]

Hi Margaret,
This may be a misunderstanding of your request, but what about:

mydata<-data.frame(oldvar=paste("topic",sample(1:9,20,TRUE),sep=""))
mydata$newvar<-sapply(mydata$oldvar,gsub,"topic.","parenttopic")

Jim


On Tue, Oct 11, 2016 at 1:56 AM, MACDOUGALL Margaret
<Margaret.MacDougall at ed.ac.uk> wrote:
> Hello
>
> The R code
> mydata$newvar[oldvar = "topic1"] <- "parenttopic"
>
> is intended to recode the category 'topic 1' of the old  varaible 'oldvar' a new category label 'parenttopic' by defining the new variable 'newvar'.
>
> Is there a convenient way to edit this code to allow me to recode a list of categories 'topic 1', 'topic 9' and 'topic 14', say, of the the old variable 'oldvar' as 'parenttopic' by means of the new variable 'newvar', while also mapping system missing values to system missing values?
>
> Thanks in advance
>
> Best wishes
> Margaret
>
>
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