Filling data frame with previous row value

Question

I have a data frame that has 2 columns.

column1 has random numbers in column2 is a place holding column for what i want column3 to look like

  random         


        

Answer 1

I suggest using the run length encoding functions, it's a natural way for dealing with steaks in a data set. Using @Kevin's example vector:

temp = c(1,0,0,0,.5,0,0,0,0,0,1,0,0,0,0,0,1,0,0.5,0,0,0,1)
y <- rle(temp)
#str(y)
#List of 2
# $ lengths: int [1:11] 1 3 1 5 1 5 1 1 1 3 ...
# $ values : num [1:11] 1 0 0.5 0 1 0 1 0 0.5 0 ...
# - attr(*, "class")= chr "rle"


for( i in seq(y$values)[-1] ) {
   if(y$values[i] == 0) {
      y$lengths[i-1] = y$lengths[i] + y$lengths[i-1]
      y$lengths[i] = 0
   }
}

#str(y)
#List of 2
# $ lengths: num [1:11] 4 0 6 0 6 0 2 0 4 0 ...
# $ values : num [1:11] 1 0 0.5 0 1 0 1 0 0.5 0 ...
# - attr(*, "class")= chr "rle"

inverse.rle(y)
#  [1] 1.0 1.0 1.0 1.0 0.5 0.5 0.5 0.5 0.5 0.5 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.5
# [20] 0.5 0.5 0.5 1.0