How to increment a value in column when a chose value id in another column

Question

I have this kind if table :

Value:

U

R

T

'*

D

E

'*

M

R

Z

.*

...

I want to create a second column with value incremented when a "*" is the first column :

Value,newcolumn:

U 1

R 1

T 1

'* 1

D 2

E 2

'* 2

M 3

R 3

Z 3

'* 3

How would you do it by not using for loop? Or what IS thé most idiomatic way for doing this ?

I will be very grateful toward any help.

Thanks.

I tried with data.frame rleid, but the count is incremented when "*" is the value columns, while I want it to be incremented just after.

My data : structure(list(value = c("U", "R", "T", "*", "D", "E", "*", "M","R", "Z", "*")), class = c("tbl_df", "tbl", "data.frame"), row.names = c(NA,-11L))

Solved (thanks to GuedesBF):

df %>% mutate(value2 = cumsum(lag(value, default = '') == '*') +1)

Answer 1

We can use rleid or cumsumon the lagged values:

library(dplyr)

df %>% mutate(value2 = paste0(value,
                              ' ',
                              cumsum(lag(value, default = '') == '*') +1))


# A tibble: 11 × 2
   value value2
   <chr> <chr> 
 1 U     U 1   
 2 R     R 1   
 3 T     T 1   
 4 *     * 1   
 5 D     D 2   
 6 E     E 2   
 7 *     * 2   
 8 M     M 3   
 9 R     R 3   
10 Z     Z 3   
11 *     * 3