diagonal value in co-occurrence matrix

Question

I am so newbie and thank you so much in advance for advice

I want to make co-occurrence matrix, and followed link below

How to use R to create a word co-occurrence matrix

but I cannot understand why value of A-A is 10 in the matirx below It should be 4 isn't it? because there are four A

dat <- read.table(text='film tag1 tag2 tag3

1 A A A
2 A C F
3 B D C ', header=T)

crossprod(as.matrix(mtabulate(as.data.frame(t(dat[, -1])))))

( ) A C F B D

A 10 1 1 0 0

C 1 2 1 1 1

F 1 1 1 0 0

B 0 1 0 1 1

D 0 1 0 1 1

score 1 · Answer 1 · answered Nov 01 '17 at 13:39

1

The solution you use presumes each tag appears only once per film, which jives with the definition of a co-occurrence matrix as far as I can tell. Therefore, each A on the first line gets counted as co-occurring with itself and with the other two As, resulting in a total of ten co-occurences when factoring in the A on the second line.

answered Nov 01 '17 at 13:39

Haem

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Thank you so much ! I got it – Charley Nov 02 '17 at 10:14
@Charley You're welcome. You can mark this answer as accepted by clicking on the checkmark icon under the vote count. – Haem Nov 02 '17 at 10:18

diagonal value in co-occurrence matrix

1 Answers1