r - calculate row sum and product in data.frame

Question

I would like to append a columns to my data.frame in R that contain row sums and products Consider following data frame

x    y     z
1    2     3
2    3     4
5    1     2

I want to get the following

x    y     z    sum    prod
1    2     3    6       6  
2    3     4    9       24 
5    1     2    8       10

I have tried

 sum = apply(ages,1,add)

but it gives me a row vector. Can some one please show me an efficient command to sum and product and append them to original data frame as shown above?

Answer 1

Try

 transform(df, sum=rowSums(df), prod=x*y*z)
 #  x y z sum prod
 #1 1 2 3   6    6
 #2 2 3 4   9   24
 #3 5 1 2   8   10

Or

 transform(df, sum=rowSums(df), prod=Reduce(`*`, df))
 #   x y z sum prod
 #1 1 2 3   6    6
 #2 2 3 4   9   24
 #3 5 1 2   8   10

Another option would be to use rowProds from matrixStats

 library(matrixStats)
 transform(df, sum=rowSums(df), prod=rowProds(as.matrix(df)))

If you are using apply

 df[,c('sum', 'prod')] <-  t(apply(df, 1, FUN=function(x) c(sum(x), prod(x))))
 df
 #  x y z sum prod
 #1 1 2 3   6    6
 #2 2 3 4   9   24
 #3 5 1 2   8   10