根据另一列的值替换列中的 NA

Question

I have a dataframe like below:

    name<-c("Fred","George","","Fred","George")
wif<-c("fd","gf",NA,NA,NA)
asv<-c("hj","fd",NA,NA,NA)
wdf<-c("bn","jk",NA,NA,NA)
label<-c("Fred","George","","Fred","George")
fam<-data.frame(name,wif,asd,wdf,label)

As you can see the first 2 rows are exactly the same with the last 2 rows but wife1 and wife2 and wife3 values are NAs . The middle has blank values and NAs and should remain like that.I want to fill the last 2 rows with the same values with the first 2 rows. Note that the solution should be applied in a dataset with different number of rows.

I tried fam %>% group_by(name) %>% mutate_all(~.[.is.na(.)]) but I get:

mutate_all()` ignored the following grouping variables:
Column `name`
Use `mutate_at(df, vars(-group_cols()), myoperation)` to silence the message.
Error: Column `wife1` must be length 1 (the group size), not 0

Answer 1

You can match the name column with itself to get the index of the first time the name occurred and use the value from that row for the columns you want to modify.

cols <- 2:4 # or if your column names contain a pattern: grep(pattern, names(fam))
fam[cols] <- fam[match(fam$name, fam$name), cols]

fam
#     name wife1 wife2 wife3  label
# 1   Fred    fd    hj    bn   Fred
# 2 George    gf    fd    jk George
# 3         <NA>  <NA>  <NA>       
# 4   Fred    fd    hj    bn   Fred
# 5 George    gf    fd    jk George

Answer 2

To make your approach to work here is one way. As stated in the error message use mutate_at and ignore groups which has no - non NA value and return them as it is.

library(dplyr)

fam %>%
  group_by(name) %>% 
  mutate_at(vars(starts_with("wife")), ~ if (any(!is.na(.))) .[!is.na(.)] else .)


#  name   wife1 wife2 wife3 label 
#  <chr>  <chr> <chr> <chr> <chr> 
#1 Fred   fd    hj    bn    Fred  
#2 George gf    fd    jk    George
#3 ""     NA    NA    NA    ""    
#4 Fred   fd    hj    bn    Fred  
#5 George gf    fd    jk    George

data

name<-c("Fred","George","","Fred","George")
wife1<-c("fd","gf",NA,NA,NA)
wife2<-c("hj","fd",NA,NA,NA)
wife3<-c("bn","jk",NA,NA,NA)
label<-c("Fred","George","","Fred","George")
fam<-data.frame(name,wife1,wife2,wife3,label, stringsAsFactors = FALSE)