R help - Jun 2021 - Need to compare two columns in two data.frames and return all rows from df where rows values are missing

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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... but I *think*

merge(A, B, by = "name", all = TRUE)

is what you want. Rows of NA's correspond to rows that were in one but not
the other.

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Sun, Jun 13, 2021 at 2:38 PM Gregg Powell via R-help <
r-help at 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______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

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 at 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______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.