R: replacing NAs in a data.frame with values in the same position in another dataframe

问题

I have a dataframe with some NA values:

dfa <- data.frame(a=c(1,NA,3,4,5,NA),b=c(1,5,NA,NA,8,9),c=c(7,NA,NA,NA,2,NA))
dfa

I would like to replace the NAs with values in the same position in another dataframe:

dfrepair <- data.frame(a=c(2:7),b=c(6:1),c=c(8:3))
dfrepair

I tried:

dfa1 <- dfa

dfa1 <- ifelse(dfa == NA, dfrepair, dfa)
dfa1

but this did not work.

回答1:

You can do:

dfa <- data.frame(a=c(1,NA,3,4,5,NA),b=c(1,5,NA,NA,8,9),c=c(7,NA,NA,NA,2,NA))
dfrepair <- data.frame(a=c(2:7),b=c(6:1),c=c(8:3))
dfa[is.na(dfa)] <- dfrepair[is.na(dfa)]
dfa

  a b c
1 1 1 7
2 3 5 7
3 3 4 6
4 4 3 5
5 5 8 2
6 7 9 3

回答2:

In the tidyverse, you can use purrr::map2_df, which is a strictly bivariate version of mapply that simplifies to a data.frame, and dplyr::coalesce, which replaces NA values in its first argument with the corresponding ones in the second.

library(tidyverse)

dfrepair %>% 
    mutate_all(as.numeric) %>%    # coalesce is strict about types
    map2_df(dfa, ., coalesce)

## # A tibble: 6 × 3
##       a     b     c
##   <dbl> <dbl> <dbl>
## 1     1     1     7
## 2     3     5     7
## 3     3     4     6
## 4     4     3     5
## 5     5     8     2
## 6     7     9     3

回答3:

We can use Map from base R to do a columnwise comparison between the two datasets

dfa[] <- Map(function(x,y) {x[is.na(x)] <- y[is.na(x)]; x}, dfa, dfrepair)
dfa
#  a b c
#1 1 1 7
#2 3 5 7
#3 3 4 6
#4 4 3 5
#5 5 8 2
#6 7 9 3

回答4:

dfa <- data.frame(a=c(1,NA,3,4,5,NA),b=c(1,5,NA,NA,8,9),c=c(7,NA,NA,NA,2,NA))
dfa
dfrepair <- data.frame(a=c(2:7),b=c(6:1),c=c(8:3))
dfrepair 
library(dplyr)
coalesce(as.numeric(dfa), as.numeric(dfrepair))

  a b c
1 1 1 7
2 3 5 7
3 3 4 6
4 4 3 5
5 5 8 2
6 7 9 3

As the code in dplyr is written in C++ it is faster in most cases. An other important advantage is that coalesce as well as many other dplyr functions are the same in SQL. Using dplyr you learn SQL by coding in R. ;-)

来源：https://stackoverflow.com/questions/41175128/r-replacing-nas-in-a-data-frame-with-values-in-the-same-position-in-another-dat

标签

dataframe