Count number of values in row using dplyr

Question

This question should have a simple, elegant solution but I can\'t figure it out, so here it goes:

Let\'s say I have the following dataset and I want to count the num

Answer 1

You can use do, which doesn't add the column to your original data frame and you need to add the column to your original data frame.

df %>%
    rowwise %>%
    do(numtwos = sum(.[-1] == 2)) %>% 
    data.frame
  numtwos
1       2
2       1
3       0
4       1
5       1

Add a cbind to bind the new column to the original data frame:

df %>%
     rowwise %>%
     do(numtwos = sum(.[-1] == 2)) %>% 
     data.frame %>% cbind(df, .)

  ID X1 X2 X3 numtwos
1  A  2  5  2       2
2  B  2  5  1       1
3  C  3  4  4       0
4  D  5  4  2       1
5  E  2  1  4       1