Dear List
I need to transform a large matrix M with many NAs into a list L with
one row for each non missing cell. Every row should contain the cell
value in the first column, and its coordinates of the matrix in column
2 and 3.
M:
x1 x2
y1 1 2
y2 4 5
y3 7 8
L:
v x y
1 1 1
4 1 2
7 1 2
2 2 1
5 2 2
8 2 3
I'm trying to do this with a loop, but since my matrix is quite large
(around 10k^2) this just takes a very long time.
There must be a more efficient and elegant way to do this. Any hints?
Thanks,
Stefan
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