Count number of unique values per row [duplicate]

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)))

Answer 2

We can also use a vectorized approach with regex. After pasteing the elements of each row of the dataset (do.call(paste0, ...), match a pattern of any character, capture as a group ((.)), using the positive lookahead, match characters only if it appears again later in the string (\\1 - backreference for the captured group and replace it with blank (""). So, in effect only those characters remain that will be unique. Then, with nchar we count the number of characters in the string.

example$count <- nchar(gsub("(.)(?=.*?\\1)", "", do.call(paste0, example), perl = TRUE))
example$count
#[1] 2 1 3 3 2 1