counts sequences in R -

id  random  count   0        -1   1         1   1         2   0        -1   0        -2   1         1   0        -1   1         1   0        -1 b   0        -1 b   0        -2 b   1         1 b   0        -1 b   1         1 b   0        -1 b   0        -2 b   0        -3 

id player , random binary 0 or 1 , want create count column counts sequences of 1's , 0's player , preferably without loops since database big.

here's dplyr solution

dat %>%   transform(idx = c(0,cumsum(random[-1l] != random[-length(random)]))) %>%   group_by(id, idx) %>%   mutate(count = -1*cumsum(random == 0) + cumsum(random == 1)) %>%   ungroup() %>%   select(-idx)  source: local data frame [17 x 3]     id random count 1        0    -1 2        1     1 3        1     2 4        0    -1 5        0    -2 6        1     1 7        0    -1 8        1     1 9        0    -1 10  b      0    -1 11  b      0    -2 12  b      1     1 13  b      0    -1 14  b      1     1 15  b      0    -1 16  b      0    -2 17  b      0    -3