Suppose I have the following two matrices, both with same number of rows

(3), but different number of columns (3 in test1, 4 in test2).

test1 <- matrix(c(1,1,0,1,0,-1,-1,-1,0),3,3,byrow=T);

test2 <- matrix( rep( 0, len=12), nrow = 3)

I label the rows and columns of the two matrices as follows:

rownames(test1) <- c("row1","row2","row3")

rownames(test2) <- c("row1","row2","row3")

colnames(test1) <- c("a","b","d")

colnames(test2) <- c("a","b","c","d")

So, if we look at the matrices, we see

test1

a b d

row1 1 1 0

row2 1 0 -1

row3 -1 -1 0

test2

a b c d

row1 0 0 0 0

row2 0 0 0 0

row3 0 0 0 0

So, we see that while both matrices have the same rows, the matrix test1

has a subset of the columns of test2. In test1, there is no column for

'c' -- have columns for 'a', 'b', 'd'.

Now, what I want to do is this -- take the information from each column

in test1, and substitute it into the same row/column in test2. The end

result should be a matrix that looks like:

a b c d

row1 1 1 0 0

row2 1 0 0 -1

row3 -1 -1 0 0

My initial though was some sort of merge by row and column, with some

funky sort of intersection, but I couldn't figure out how to get that to

work.

Any suggestions/pointers to the obvious most appreciated.

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