R: How to replace NA with most recent value by row

Question

Assume I have the following df:

df <- data.frame(day = c(1:8), value= c(10, 25, NA, 7, NA, NA, 20, NA))

    Day     Value
1     1        10
2     2        25
3     3        NA
4     4         7
5     5        NA
6     6        NA
7     7        20
8     8        NA

I'm looking for a solution to replace NA in 'Value' column with the most recent previous non-NA value. The desired output will be:

    Day     Value
1     1        10
2     2        25
3     3        25
4     4         7
5     5         7
6     6         7
7     7        20
8     8        20

Does this answer your question? [R: fill down multiple columns](https://stackoverflow.com/questions/37648980/r-fill-down-multiple-columns) — Sinh Nguyen, Apr 13 '21 at 05:55

score 3 · Answer 1 · answered Apr 13 '21 at 08:38

In base you can use ave in combination with cumsum to fill down.

df$value <- ave(df$value, cumsum(!is.na(df$value)), FUN = function(x) x[1])
df
#  day value
#1   1    10
#2   2    25
#3   3    25
#4   4     7
#5   5     7
#6   6     7
#7   7    20
#8   8    20

score 0 · Accepted Answer · answered Apr 13 '21 at 05:59

0

There are a series of non-base solutions:

zoo::na.locf(df$Value)
data.table::nafill(df$Value)

naniar is also a package that is completely designed surrounding NA handling.

answered Apr 13 '21 at 05:59

Daniel V

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R: How to replace NA with most recent value by row

2 Answers2