Create conditional sequence in dataframe in R

Question

Looking to fill a matrix with a conditional sequence. There are multiple breaks in the data but these breaks/spaces must be maintained.

Here is a sample matrix for what I am trying to accomplish. The first column is the original data. The second column is what I am trying to create.

try <- matrix(c(rep(0,4),rep(1,3),rep(0,2),rep(1,2), rep(0,4), seq(1,3,1), rep(0,2), seq(4,5,1)),ncol=2)

I have tried using seq_long, while loop, etc. but cannot seem to get it working. Any help/pointers would be appreciated.

Answer 1

Maybe the following two steps solution is what you want.

try[, 2] <- ave(try[, 1], try[, 1], FUN = seq_along)
try[try[, 1] == 0, 2] <- 0

try[, 2]
#[1] 0 0 0 0 1 2 3 0 0 4 5

A one-liner is

ave(try[, 1], try[, 1], FUN = function(x) if(any(x == 0)) x else seq_along(x))
#[1] 0 0 0 0 1 2 3 0 0 4 5