Count of unique elements of each row in a data frame in R

Question

I have a data frame like below:

Group1  Group2  Group3  Group4
A       B       A       B   
A       C       B       A   
B       B       B       B   
A               


        

Answer 1

We can use apply with MARGIN =1 to loop over the rows

df1$Count <- apply(df1, 1, function(x) length(unique(x)))
df1$Count
#[1] 2 3 1 4 3

---

Or using tidyverse

library(dplyr)
df1 %>%
    rowwise() %>%
    do(data.frame(., Count = n_distinct(unlist(.))))
# A tibble: 5 × 5
#   Group1 Group2 Group3 Group4 Count
#*         
#1      A      B      A      B     2
#2      A      C      B      A     3
#3      B      B      B      B     1
#4      A      C      B      D     4
#5      A      D      C      A     3

---

We can also use regex to do this in a faster way. It is based on the assumption that there is only a single character per each cell

nchar(gsub("(.)(?=.*?\\1)", "", do.call(paste0, df1), perl = TRUE))
#[1] 2 3 1 4 3

More detailed explanation is given here