Search code examples
rvariable-assignment

Assign value to column based on another character column

I have a data frame that look like this:

    df <- data.frame(subject = c(a1_1, a1_1, a1_1, a1_1, a1_2, a1_2, b1_1, b1_1),
 group = c(1, NA, NA, NA, NA, 1, NA, NA, 2, NA)

as you can see only the first entry of every subject has a group assigned. My idea is fill the blank spaces of every subject with the group number(e.g. all a1_1 must have a group 1 value).

Thanks for your help!

Solution

  • We may do

    df$group <- match(df$subject, unique(df$subject))

    -output

    > df
   subject group
1     a1_1     1
2     a1_1     1
3     a1_1     1
4     a1_1     1
5     a1_2     2
6     a1_2     2
7     b1_1     3
8     b1_1     3
9     b1_1     3
10    b1_1     3

    data

    df <- structure(list(subject = c("a1_1", "a1_1", "a1_1", "a1_1", "a1_2", 
"a1_2", "b1_1", "b1_1", "b1_1", "b1_1")), class = "data.frame", row.names = c(NA, 
-10L))