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             


        

Answer 1

Only a partial answer, but if all values are greater than or equal to 0, rowSums/rowsum can be used to calculate products:

df <- data.frame(x = c(1, 2, 5), y = c(2, 3, 1), z = c(3, 4, 2))

# custom row-product-function
my_rowprod <- function(x) exp(rowSums(log(x)))

df$prod <- my_rowprod(df)
df

The generic version is (including negatives):

my_rowprod_2 <- function(x) {
  sign <- ifelse((rowSums(x < 0) %% 2) == 1, -1, 1)
  prod <- exp(rowSums(log(abs(x)))) * sign
  prod
}
df$prod <- my_rowprod_2(df)
df