Hello all!
I would like to get a diced/sliced/indexed piddle that is derived from a
larger matrix based on rows indicated by a mask.
For example, lets say I have a mask and I want to dice a matrix's rows
where the mask has a value of 1 (in any location):
pdl> p $mask = random(10)->transpose > 0.5
[
[0]
[0]
[1]
[0]
[1]
[1]
[1]
[0]
[1]
[0]
]
and lets say that this is the origin matrix I want to dice:
pdl> p $target = sequence(5, 10)
[
[ 0 1 2 3 4]
[ 5 6 7 8 9]
[10 11 12 13 14]
[15 16 17 18 19]
[20 21 22 23 24]
[25 26 27 28 29]
[30 31 32 33 34]
[35 36 37 38 39]
[40 41 42 43 44]
[45 46 47 48 49]
]
I would like to have a result that has only the rows where the mask is
marked with a 1, like this:
$result = filter_somehow_from($target by $mask);
[
[30 31 32 33 34]
[35 36 37 38 39]
[40 41 42 43 44]
[45 46 47 48 49]
]
so I can modify the result in-place, like square it:
$result **= 2;
[ 900 961 1024 1089 1156]
[1225 1296 1369 1444 1521]
[1600 1681 1764 1849 1936]
[2025 2116 2209 2304 2401]
so the `**= 2` will modify to the original matrix:
[
[ 0 1 2 3 4]
[ 5 6 7 8 9]
[10 11 12 13 14]
[15 16 17 18 19]
[20 21 22 23 24]
[25 26 27 28 29]
[ 900 961 1024 1089 1156]
[1225 1296 1369 1444 1521]
[1600 1681 1764 1849 1936]
[2025 2116 2209 2304 2401]
]
I know I could do something with ->slice to modify in-place, but ':,6:9' is not
$mask:
pdl> p $target->slice(':,6:9') **= 2
[
[ 900 961 1024 1089 1156]
[1225 1296 1369 1444 1521]
[1600 1681 1764 1849 1936]
[2025 2116 2209 2304 2401]
]
pdl> p $target
[
[ 0 1 2 3 4]
[ 5 6 7 8 9]
[ 10 11 12 13 14]
[ 15 16 17 18 19]
[ 20 21 22 23 24]
[ 25 26 27 28 29]
[ 900 961 1024 1089 1156]
[1225 1296 1369 1444 1521]
[1600 1681 1764 1849 1936]
[2025 2116 2209 2304 2401]
]
So $mask defines the rows I need to modify, and $mask could have 1's in
any location, and those are the locations I need to twiddle.
Ideas?
Thanks for your help!
--
Eric Wheeler
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