I like to fill data.frames like
key val
"A" 2
NA 9
NA 5
"B" 5
NA 1
"C" 6
NA 9
NA 1
NA 0
NA 1
with the "above" key instead of NA
key val
"A" 2
"A" 9
"A" 5
"B" 5
"B" 1
"C" 6
"C" 9
"C" 1
"C" 0
"C" 1
I can go through each line per hand and save the last valid key, but that is very slow. Do you know a efficient way? Perhaps with dplyr?
Thank you very much