Hello forum,
currently I try to make use of the Fold family of primitives to achieve
a rather simple (I think) task. However, I have not been able to reach
the desired goal. This is, what I want to do:
Suppose, I have some matrix M and some vector V:
M =: 3 4 $ 12?12
V =: 1 2 3
I now want to apply each element of V to the whole of M (an operation
which is supposed to give a result with the same size of M). I want to
give a short exemplary demonstration of the data flow I imagine:
M => Start
7 4 11 3
0 1 6 10
9 2 5 8
M1 => (M e. 0 { V)
0 0 0 0
0 1 0 0
0 0 0 0
M2 => (M e. 1 { V)
0 0 0 0
0 0 0 0
0 1 0 0
M3 => (M e. 2 { V)
0 0 0 1
0 0 0 0
0 0 0 0
Result => M1 + M2 + M3
0 0 0 1
0 1 0 0
0 1 0 0
To me it seems, that this would be a task for the Fold family of
primitives, but I don’t seem to be able to get my head around this.
I’d very much appreciate any hints on how to implement this with Fold
- and of course I’d like to know, whether my intuition, that the Fold
family would be the right tool for the job, is right or if there are
better options.
Happy holidays to everyone and kind regards,
Thomas
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