CODEWITHSUNDEEP
rdataframeadjacency-matrix
user2246905
user2246905

Reputation: 1039

create weighted adjacency matrix from data frame R

I have a data frame of the following way

dat <- data.frame(A=c("D", "A", "D", "B"), B=c("B", "B", "D", "R"), C=c("A", "D", "C", ""), D=c("D", "C", "A", "A"))

My idea is to create a matrix with this information, based on the number of occasions that each column variable refers to the other columns (and ignore when referring to other things that are not in one of the columns (e.g. "R")). So I want to fill the following matrix:

n <- ncol(dat)
names_d <- colnames(dat)
mat <- matrix(0, nrow=n, ncol=n)
rownames(mat) <- names_d
colnames(mat) <- names_d

So in the end, I would have something like this:

  A B C D
A 1 1 0 2
B 0 2 0 1
C 1 0 1 1
D 2 0 1 1

Which would be the most efficient way of doing this in R?

Upvotes: 1

Views: 200

Answers (2)

akrun
akrun

Reputation: 887118

Another option is stack with table

 table(subset(stack(dat), nzchar(values) & values != 'R'))

Upvotes: 1

ThomasIsCoding
ThomasIsCoding

Reputation: 101373

You can try the code below

> t(sapply(dat, function(x) table(factor(x, levels = names(dat)))))
  A B C D
A 1 1 0 2
B 0 2 0 1
C 1 0 1 1
D 2 0 1 1

or

> t(xtabs(~., subset(stack(dat), values != "")))
   values
ind A B C D
  A 1 1 0 2
  B 0 2 0 1
  C 1 0 1 1
  D 2 0 1 1

Upvotes: 3

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