Good morning,
I am merging two datasets and I would like to save the non-matching rows
in a separate file.
The problem is how to retrieve the non-matching rows in R.
Example:
DATASET A
code nomi
A1 Franco
A2 Mario
A3 Andrea
A4 Sandro
A5 Luca
DATASET B
code book
A1 Guerra e Pace
A1 Storia di Roma
A2 La coscienza di Zeno
A4 Ivanhoe
A1 I Malavoglia
A2 Jude the obscure
when merging two rows are unmatched:
A3 Andrea
A5 Luca
And these are exactly the rows I would like to store in a separate
file/dataset.
I tried with:
AM<-merge(A,B,all=TRUE)
A1<-AM[is.na(AM$book),]
to keep the rows with a NA value in the book column.
The problem is that this works in this particular case, but in real
situations I might have other NA values in the book column, not
resulting from the merge operation, but that are real missing values: in
such cases, with the is.na command I would retrieve also thiese unneeded
rows.
Can someone suggest a better strategy to tackle this problem?
Regards,
Filippo Biscarini
Wageningen University
The Netherlands
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