dataframe - Replace missing values in a vector with the last value that was not missing in R -

i trying import table web page using readhtmltable function, first few rows of data looks when in r.

              event                athlete country      result  medal year 1          100m men              tom burke     usa        12.0   gold 1896 2                            fritz hofmann     deu   12.2 est. silver 1896 3                             francis lane     usa        12.6 bronze 1896 4                          alajos szokolyi     hun   12.6 est. bronze 1896 5          400m men              tom burke     usa        54.2   gold 1896 6                          herbert jamison     usa         n/a silver 1896 7                           charles gmelin     gbr         n/a bronze 1896 8          800m men            teddy flack     aus      2:11.0   gold 1896 9                            nֳ¡ndor dֳ¡ni     hun 2:11.8 est. silver 1896 10                       demitrios golemis     gre         n/a bronze 1896 

now if @ event column can see of rows of event field empty, way table on website, looking efficient way fill blanks @ end should this

              event       athlete      country      result  medal year 1          100m men       tom burke       usa        12.0   gold 1896 2          100m men       fritz hofmann   deu   12.2 est. silver 1896 3          100m men       francis lane    usa        12.6 bronze 1896 4          100m men       alajos szokolyi hun   12.6 est. bronze 1896 5          400m men       tom burke       usa        54.2   gold 1896 

basically every time field in event column empty need fill last value not empty. column saved in r factor , know technically can using loop , going on of vector elements time consuming considering fat there 300000 rows in table. hoping more efficient

here's toy example of how purrr package used solve problem, assuming data in data.frame , missing values na:

library(purrr)  df <- data.frame("event" = c(1, na, 2, na, 3, na, 5), "other" = 1:7)  df #     event other # 1     1     1 # 2    na     2 # 3     2     3 # 4    na     4 # 5     3     5 # 6    na     6 # 7     5     7   df$event <- accumulate(.x = df$event, .f = function(x, y) { if(is.na(y)) x else y })  df #     event other # 1     1     1 # 2     1     2 # 3     2     3 # 4     2     4 # 5     3     5 # 6     3     6 # 7     5     7