Multiply a data frame row-by-row

Question

Input file:

df1 <- data.frame(row.names=c(\"w\",\"x\",\"y\",\"z\"), 
                  A=c(0,0,0,0),
                  B=c(0,1,0,0), 
                  C=c(1,         


        

Answer 1

A shorter way (I think) using the amazing plyr package

Your data.frame

df1 <- data.frame(row.names=c("w","x","y","z"), A=c(0,0,0,0), B=c(0,1,0,0), C=c(1,0,1,0), D=c(1,1,1,1))

YOUR_COMBS<-combn(rownames(df1),2)

And your result :)

require(plyr) #(version 1.81...in version 1.82 you can take the annoying 'X1' index out... )


     YOUR_RESULTS<-adply(YOUR_COMBS,2,function(x) {
      tmp_row<-data.frame(Comb=paste0(x,collapse = ''),df1[x[1],]*df1[x[2],])
 })