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

Here is an interesting way with the Reduce function.

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)
fill_zero = function(x,y) if(y==0) x else y
state = Reduce(fill_zero, temp, accumulate=TRUE)

If you're worried about speed, you can try Rcpp.

library(Rcpp)
cppFunction('
  NumericVector fill_zeros( NumericVector x ) {
    for( int i=1; i