Partially merge two datasets and fill in NAs in R -

i have 2 datasets

a = raw dataset thousands of observations of different weather events

   state       evtype 1     al winter storm 2     al      tornado 3     al    tstm wind 4     al    tstm wind 5     al    tstm wind 6     al         hail 7     al    high wind 8     al    tstm wind 9     al    tstm wind 10    al    tstm wind 

b = dictionary table, has standard spelling weather events.

                    evtype       evmatch 1    high surf advisory          <na> 2         coastal flood coastal flood 3           flash flood   flash flood 4             lightning     lightning 5             tstm wind          <na> 6       tstm wind (g45)          <na> 

both merged df_new evtype

library(dplyr) df_new <- left_join(a, b, = c("evtype"))     state       evtype           evmatch 1     al winter storm      winter storm 2     al      tornado              na 3     al    tstm wind thunderstorm wind 4     al    tstm wind thunderstorm wind 5     al    tstm wind thunderstorm wind 6     al         hail              na 7     al    high wind         high wind 8     al    tstm wind thunderstorm wind 9     al    tstm wind thunderstorm wind 10    al    tstm wind thunderstorm wind 11    al   heavy rain        na 12    al  flash flood       na 13    al    tstm wind thunderstorm wind 14    al   heavy rain        na 15    al    tstm wind thunderstorm wind 

fill in missing nas

as can see in df_new$evmatch, there nas. how can merge dataset, have na's in evmatch filled in corresponding word evtype. example...

wanted output

 state       evtype           evmatch 1     al winter storm      winter storm 2     al      tornado           tornado 3     al    tstm wind thunderstorm wind 4     al    tstm wind thunderstorm wind 5     al    tstm wind thunderstorm wind 6     al         hail              hail 7     al    high wind         high wind 8     al    tstm wind thunderstorm wind 9     al    tstm wind thunderstorm wind 10    al    tstm wind thunderstorm wind 11    al   heavy rain        heavy rain 12    al  flash flood       flash flood 13    al    tstm wind thunderstorm wind 14    al   heavy rain        heavy rain 15    al    tstm wind thunderstorm wind 

answers given in comments question:

1: using base r

method 1:

df_new$evmatch <- with(df_new, ifelse(is.na(evmatch), evtype, evmatch)) 

method 2:

df_new$evmatch[is.na(df_new$evmatch] <- df_new$evtype[is.na(df_new$evmatch] 

note: make sure both vars characters or erroneous results occur. if needed transform as.character.

2: using data.table

library(data.table) setdt(df_new)[is.na(evmatch), evmatch := evtype] 

3: using dplyr

library(dplyr) filter(df_new, is.na(evmatch) %>%           select(evmatch) <- filter(df_new, is.na(evmatch) %>%                                       select(evtype)