基于r中特定字符串更改的增量变量

Question

I am looking to create a variable that increments when specific strings appear in a column. If strings "x", "y", or "z" appear in Event, I want the sequence to increment, otherwise I would like it to stay constant. Any help would be appreciated! See table below:

    Event   Seq
1     a      1
2     b      1
3     x      2
4     c      2
5     a      2
6     b      2
7     y      3
8     a      3
9     z      4
10    b      4
11    y      5
12    a      5
13    b      5

Answer 1

This for loop can update the Seq as you requested in your question:

for(i in 1:nrow(df)){
  if(df$Event[i] %in% c('x','y','z')){
    df$Seq[i] <- df$Seq[i] + 1
  }
}

> df
   Event Seq
1      a   1
2      b   1
3      x   3
4      c   2
5      a   2
6      b   2
7      y   4
8      a   3
9      z   5
10     b   4
11     y   6
12     a   5
13     b   5