Hi Bryan and Luis, thanks for your quick response! Both suggestions look
great and I learned a few things about PDL like which, whereND, and
dice_axis that I hadn't before.
Cheers,
--
Eric Wheeler
On Wed, 9 Aug 2023, Luis Mochan wrote:
>
> You could use whereND, as:
> 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]
> ]
>
> Set a 1D mask
> pdl> p $mask=random(10)>0.5
> [1 0 0 1 1 0 1 1 1 0]
> Use mask to select elements. Notice the transpositions (here with mv)
> so that mask corresponds to rows, not to columns.
> pdl> p $target->mv(0,1)->whereND($mask)->mv(1,0)
> [
> [ 0 1 2 3 4]
> [15 16 17 18 19]
> [20 21 22 23 24]
> [30 31 32 33 34]
> [35 36 37 38 39]
> [40 41 42 43 44]
> ]
> Operate on selected rows.
> pdl> p $target->mv(0,1)->whereND($mask)->mv(1,0)**=2
> [
> [ 0 1 4 9 16]
> [ 225 256 289 324 361]
> [ 400 441 484 529 576]
> [ 900 961 1024 1089 1156]
> [1225 1296 1369 1444 1521]
> [1600 1681 1764 1849 1936]
> ]
> Print the modified target
> pdl> p $target
> [
> [ 0 1 4 9 16]
> [ 5 6 7 8 9]
> [ 10 11 12 13 14]
> [ 225 256 289 324 361]
> [ 400 441 484 529 576]
> [ 25 26 27 28 29]
> [ 900 961 1024 1089 1156]
> [1225 1296 1369 1444 1521]
> [1600 1681 1764 1849 1936]
> [ 45 46 47 48 49]
> ]
>
> Regards,
> Luis
>
>
> On Wed, Aug 09, 2023 at 12:10:09AM -0700, Eric Wheeler wrote:
> > 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
> >
> >
> > _______________________________________________
> > pdl-general mailing list
> > pdl-general@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/pdl-general
> >
>
> --
>
> o
> W. Luis Mochán, | tel:(52)(777)329-1734 /<(*)
> Instituto de Ciencias Físicas, UNAM | fax:(52)(777)317-5388 `>/ /\
> Av. Universidad s/n CP 62210 | (*)/\/ \
> Cuernavaca, Morelos, México | moc...@fis.unam.mx /\_/\__/
> GPG: 791EB9EB, C949 3F81 6D9B 1191 9A16 C2DF 5F0A C52B 791E B9EB
> _______________________________________________
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