CODEWITHSUNDEEP
rindexingmatching
qwertylpc
qwertylpc

Reputation: 2106

Finding rows which match between 2 dataframes, and the index of them in R

I have 2 dataframes. First (and I know how to do this) I want to find which rows (the whole row) match between the 2 dataframes. So I can create a column in A which tells me if that entire row is in B. However, the part I don't know how to do is to find which indices in B it would be.

TL DR; I need to create a new column in A, which tells me FALSE if the whole row isn't in B, or instead give me the index of where that row is in B.

a = as.data.frame(matrix(data = 1:10,nrow=5))
b = as.data.frame(matrix(data = c(1:5,10,7,6,9,8), nrow=5))

set.seed(02138)
b = b[sample(nrow(b)),]
rownames(b) = 1:nrow(b)
a_ = do.call("paste", a[,1:2])
b_ = do.call("paste", b[,1:2])

# Gets me TRUE/FALSE of whether there is a complete row-wise match
a$InB = a_ %in% b_

# Gets me which rows they are in b
b[b_ %in% a_,]

# Now is where I need help combining this
# Expected output

> a$InB = temp
> a
  V1 V2   InB
1  1  6 FALSE
2  2  7     3
3  3  8 FALSE
4  4  9     5
5  5 10 FALSE

Upvotes: 2

Views: 2032

Answers (1)

Pierre L
Pierre L

Reputation: 28441

You can add this:

a$InB[a$InB] <- as.character(which(b_ %in% a_))
a
#  V1 V2   InB
#1  1  6 FALSE
#2  2  7     3
#3  3  8 FALSE
#4  4  9     5
#5  5 10 FALSE

Upvotes: 5

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