You can use the following methods to replace NA values with the mean using functions from the dplyr and tidyr packages in R:

Method 1: Replace NA values with Mean in One Column

df %>% mutate(across(col1, ~replace_na(., mean(., na.rm=TRUE))))

Method 2: Replace NA values with Mean in Several Columns

df %>% mutate(across(c(col1, col2), ~replace_na(., mean(., na.rm=TRUE))))

Method 3: Replace NA values with Mean in All Numeric Columns

df %>% mutate(across(where(is.numeric), ~replace_na(., mean(., na.rm=TRUE))))

The following examples show how to use each method in practice with the following data frame:

#create data frame
df <- data.frame(player=c('A', 'B', 'C', 'D', 'E'),
                 points=c(17, 13, NA, 9, 25),
                 rebounds=c(3, 4, NA, NA, 8),
                 blocks=c(1, 1, 2, 4, NA))

#view data frame
df

  player points rebounds blocks
1      A     17        3      1
2      B     13        4      1
3      C     NA       NA      2
4      D      9       NA      4
5      E     25        8     NA

Example 1: Replace NA Values with Mean in One Column

The following code shows how to replace the NA values in the points column with the mean value of the points column:

library(dplyr)
library(tidyr)

#replace NA values in points column with mean of points column
df <- df %>% mutate(across(points, ~replace_na(., mean(., na.rm=TRUE))))
#view updated data frame
df

  player points rebounds blocks
1      A     17        3      1
2      B     13        4      1
3      C     16       NA      2
4      D      9       NA      4
5      E     25        8     NA

The mean value in the points column was 16, so the one NA value in the points column was replaced with 16.

All other columns remained unchanged.

Example 2: Replace NA Values with Mean in Several Columns

The following code shows how to replace the NA values in the points  and blocks columns with their respective column means:

library(dplyr)
library(tidyr)

#replace NA values in points and blocks columns with their respective means
df <- df %>% mutate(across(c(points, blocks), ~replace_na(., mean(., na.rm=TRUE))))
#view updated data frame
df

  player points rebounds blocks
1      A     17        3      1
2      B     13        4      1
3      C     16       NA      2
4      D      9       NA      4
5      E     25        8      2

Example 3: Replace NA Values with Mean in All Numeric Columns

The following code shows how to replace the NA values in every numeric columns with their respective mean value:

library(dplyr)
library(tidyr)

#replace NA values in all numeric columns with their respective means
df <- df %>% mutate(across(where(is.numeric), ~replace_na(., mean(., na.rm=TRUE))))

#view updated data frame
df

  player points rebounds blocks
1      A     17        3      1
2      B     13        4      1
3      C     16        5      2
4      D      9        5      4
5      E     25        8      2

Notice that the NA values in all numeric columns have been replaced with their respective column means.

The one column that was not numeric (player) has remained unchanged.

The following tutorials explain how to perform other common tasks in dplyr: