[R] Need to compare two columns in two data.frames and return all rows from df where rows values are missing

[William Michels]

Maybe something like this?

> df_A <- data.frame(names=LETTERS[1:10], values_A=1:10)
> df_B <- data.frame(names=LETTERS[6:15], values_B=11:20)
> df_AB <- merge(df_A, df_B, by="names")
> df_AAB <- merge(df_A, df_AB, all.x=TRUE)
> df_BAB <- merge(df_B, df_AB, all.x=TRUE)
> df_C <- df_AAB[is.na(df_AAB$values_B), ]
> df_D <- df_BAB[is.na(df_BAB$values_A), ]
> df_AB
  names values_A values_B
1     F        6       11
2     G        7       12
3     H        8       13
4     I        9       14
5     J       10       15
> df_C
  names values_A values_B
1     A        1       NA
2     B        2       NA
3     C        3       NA
4     D        4       NA
5     E        5       NA
> df_D
   names values_B values_A
6      K       16       NA
7      L       17       NA
8      M       18       NA
9      N       19       NA
10     O       20       NA
>

HTH, Bill.

W. Michels, Ph.D.











On Sun, Jun 13, 2021 at 2:38 PM Gregg Powell via R-help
<r-help using r-project.org> wrote:
>
> This is even complicated to write into a question....
>
> Have two data.frames (A and B)
>
> data.frame A and B each have a name column. Want to compare A and B data.frame to each other based on the values in the 'names' columns - for every name that appears in dataframe A  but not B, I want to copy the corresponding rows to a third dataframe C, and for every name that appears in B but not A, I want to copy the corresponding rows to a fourth dataframe D. I can then row bind the dataframes C and D together and get a complete list of all the rows that were missing in either A or B.
>
> try as I might - I can't get this to work. Can someone help P-L-E-A-S-E!!!!
>
>
>  Thanks,
>  Gregg Powell
>  AZ, USA______________________________________________
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