Joe,
When you have a dyadic verb (one which takes both a left and a right argument),
and you want to apply that verb to different size pieces ("cells") of the
arguments, use the rank conjunction " .
In your case, you want to pair the rows of the left argument with the table of
the right argument. Rows have one dimension, and so are rank 1 , tables
have two dimensions, and so are rank 2 . Consequently, you want to do:
short_data =: }:"1 data
short_data x"1 2 yuvmat
which results in an N by 3 table, where N is #data . I, personally,
would write:
short_data x"_1 _ yuvmat
which means "pair the /items/ of the left argument with the /entire/ of the
right argument.". The items of short_data happen to be rows, and the entire
of yuvmat happens to be a table. The results are unchanged.
Essentially, what " does is pair up the requested parts ("cells") of the two
arguments, then applies the verb between them. That is, for each item (row) in
short_data, it takes a copy of the entire (table) yuvmat, and matrix-multiplies
the two. You can experiment with other cells:
show_pairings =: ,&:<
short_data show_pairings"1 2 yuvmat
short_data show_pairings"_1 _ yuvmat
short_data show_pairings"0 2 yuvmat
short_data show_pairings"1 0 yuvmat
Hope this helps,
-Dan
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