Using ifelse Within apply

Question

I am trying to make a new column in my dataset give a single output for each and every row, depending on the inputs from pre-existing columns.

In this output column, I d

Answer 1

You want to check if any of the variables in a row are 0, so you need to use any(x==0) instead of x == 0 in the ifelse statement:

apply(data, 1, function(x) {ifelse(any(x == 0), NA, length(unique(x)))})
# [1]  1 NA  2

Basically ifelse returns a vector of length n if its first argument is of length n. You want one value per row, but are passing more than one with x==0 (the number of values you're passing is equal to the number of columns in your data frame).

Data:

(data <- data.frame(a=c(1, 2, 3), b=c(1, 0, 1)))
#   a b
# 1 1 1
# 2 2 0
# 3 3 1