Reshaping a data.frame so a column containing multiple features becomes multiple binary columns

Question

I have a dataframe like this

df <-data.frame(id = c(1,2),
                value = c(25,24),
                features = c(\"A,B,D,F\",\"C,B,E\"))

print(df)

i         


        

Answer 1

This is yet another use case for merge after suitable transformation.

library(reshape2)
f<-with(df,stack(setNames(strsplit(as.character(features),","),id)))
d<-dcast(f,ind~values,length,value.var="ind")
out<-merge(df[,1:2],d,by.x="id",by.y="ind")

print(out)

  id value A B C D E F
1  1    25 1 1 0 1 0 1
2  2    24 0 1 1 0 1 0

This can also be done using only default libraries (without reshape2) in a variety of slightly messier ways. In the above, you can substitute the d and out lines with the following instead:

d<-xtabs(count~ind+values,transform(f,count=1))
out<-merge(df[,1:2],as.data.frame.matrix(d),by.x="id",by.y="row.names")