R Merging Unequal Data Frames & Replacing NA with Zero (Example Code)

On this page, I’ll show how to join two unequal data frames and replace missing values by zero in the R programming language.

Creation of Example Data

df1 <- data.frame(IDs = 1:6,    # Example data frame No 1
                  col1 = 13:8,
                  col2 = 8:3,
                  col3 = 11:16)
df1                             # Structure of first data
#   IDs col1 col2 col3
# 1   1   13    8   11
# 2   2   12    7   12
# 3   3   11    6   13
# 4   4   10    5   14
# 5   5    9    4   15
# 6   6    8    3   16
df2 <- data.frame(IDs = 4:9,    # Example data frame No 2
                  var1 = 15:20,
                  var2 = 10:5)
df2                             # Structure of second data
#   IDs var1 var2
# 1   4   15   10
# 2   5   16    9
# 3   6   17    8
# 4   7   18    7
# 5   8   19    6
# 6   9   20    5

Example: Merge & Replace NA with 0

df_all <- merge(df1, df2,       # Merging df1 & df2
                by = "IDs",
                all = TRUE)
df_all                          # Printing merged data
#   IDs col1 col2 col3 var1 var2
# 1   1   13    8   11   NA   NA
# 2   2   12    7   12   NA   NA
# 3   3   11    6   13   NA   NA
# 4   4   10    5   14   15   10
# 5   5    9    4   15   16    9
# 6   6    8    3   16   17    8
# 7   7   NA   NA   NA   18    7
# 8   8   NA   NA   NA   19    6
# 9   9   NA   NA   NA   20    5
df_all[is.na(df_all)] <- 0      # Replace NA with zero
df_all                          # Printing merged data after replacing NA with zero
#   IDs col1 col2 col3 var1 var2
# 1   1   13    8   11    0    0
# 2   2   12    7   12    0    0
# 3   3   11    6   13    0    0
# 4   4   10    5   14   15   10
# 5   5    9    4   15   16    9
# 6   6    8    3   16   17    8
# 7   7    0    0    0   18    7
# 8   8    0    0    0   19    6
# 9   9    0    0    0   20    5

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