Count number of unique values per row [duplicate]

Question

I want to count the number of unique values per row.

For instance with this data frame:

example <- data.frame(var1 = c(2,3,3,2,4,5), 
                  var2 = c(2,3,5,4,2,5), 
                  var3 = c(3,3,4,3,4,5))

I want to add a column which counts the number of unique values per row; e.g. 2 for the first row (as there are 2's and 3's in the first row) and 1 for the second row (as there are only 3's in the second row).

Does anyone know an easy code to do this? Up until now I only found code for counting the number of unique values per column.

Answer 1

This apply function returns a vector of the number of unique values in each row:

apply(example, 1, function(x)length(unique(x)))

You can append it to your data.frame using on of the following two ways (and if you want to name that column as count):

example <- cbind(example, count = apply(example, 1, function(x)length(unique(x))))

or

example$count <- apply(example, 1, function(x)length(unique(x)))