Assign consecutive trial numbers to data frame beginning at match-CodePudding

I want to assign consecutive trial numbers (1-16) to a long dataframe depending on certain values of other variables.

It should look like this (simplified):

value   trial_no
videoA      1
other       1
videoB      2
other       2
other       2
videoC      3
...

This basically does what I want, but it just assigns the row numbers.

df2 <- df1 %>%
  mutate(trial_no = case_when(grepl('video', value) ~ row_number())) %>%
  fill(trial_no)

This might do what I want, but yet it assigns 16 to all.

for (vid in c(1:16)) {
  df2 <- df1 %>%
    mutate(trial_no = case_when(grepl("video", value) ~ vid)) %>%
    fill(trial_no) 
}

I'm pretty sure there is an easy solution to this. Any help is very much appreciated.

CodePudding user response：

Using grepl and count the TRUEs

transform(dat, trial_no=cumsum(grepl('video', value)))
#    value trial_no
# 1 videoA        1
# 2  other        1
# 3 videoB        2
# 4  other        2
# 5  other        2
# 6 videoC        3

Data:

dat <- structure(list(value = c("videoA", "other", "videoB", "other", 
"other", "videoC")), class = "data.frame", row.names = c(NA, 
-6L))