Here is an excerpt from an R data.frame which consist of indicators. It can be seen that for some rows the indictors switch to 1 until the end of the row while others switch back to zero.
[,18] [,19] [,20] [,21] [,22] [,23] [,24]
[1,] 0 0 0 0 0 0 0
[2,] 0 0 0 0 1 1 1
[6,] 0 0 0 0 0 0 0
[7,] 0 0 1 0 0 1 1
[8,] 0 0 0 0 0 0 0
[9,] 0 1 0 1 1 1 1
[10,] 1 1 1 1 1 1 1
[11,] 1 0 1 1 0 1 1
I want to identify the point in each row when a sequence of 1 does not change back to zero anymore to the end of the row. This should be indicated by all elements set to 1 after this point, while the previous elements are 0. The result would be:
[,18] [,19] [,20] [,21] [,22] [,23] [,24]
[1,] 0 0 0 0 0 0 0
[2,] 0 0 0 0 1 1 1
[6,] 0 0 0 0 0 0 0
[7,] 0 0 0 0 0 1 1
[8,] 0 0 0 0 0 0 0
[9,] 0 0 0 1 1 1 1
[10,] 1 1 1 1 1 1 1
[11,] 0 0 0 0 0 1 1
You can take the cumulative min from the end of each row:
t(apply(m, 1, function(r) rev(cummin(rev(r)))))
# [,1] [,2] [,3] [,4] [,5] [,6] [,7]
#[1,] 0 0 0 0 0 0 0
#[2,] 0 0 0 0 1 1 1
#[3,] 0 0 0 0 0 0 0
#[4,] 0 0 0 0 0 1 1
#[5,] 0 0 0 0 0 0 0
#[6,] 0 0 0 1 1 1 1
#[7,] 1 1 1 1 1 1 1
#[8,] 0 0 0 0 0 1 1
Data: m is an integer matrix consisting of 1 and 0
dput(m)
structure(c(0L, 0L, 0L, 0L, 0L, 0L, 1L, 1L, 0L, 0L, 0L, 0L, 0L,
1L, 1L, 0L, 0L, 0L, 0L, 1L, 0L, 0L, 1L, 1L, 0L, 0L, 0L, 0L, 0L,
1L, 1L, 1L, 0L, 1L, 0L, 0L, 0L, 1L, 1L, 0L, 0L, 1L, 0L, 1L, 0L,
1L, 1L, 1L, 0L, 1L, 0L, 1L, 0L, 1L, 1L, 1L), .Dim = c(8L, 7L))