On Sat, May 29, 2010 at 10:07 AM, Chris Marshall <[email protected]> wrote:
> It looks like you have #Var #Day-by-#Cell arrays, e.g.:
>
> PDL> $var1 = pdl q[ 111 121 131 ; 211 221 231 ]
> PDL> $var2 = pdl q[ 112 122 132 ; 212 222 232 ]
> PDL> $var3 = pdl q[ 113 123 133 ; 213 223 233 ]
> PDL> $var4 = pdl q[ 114 124 134 ; 214 224 234 ]
>
> so in this case V=#Var=4, D=#Day=3, C=#Cell=2 and you
> have 4 3x2 $varN arrays. Ignoring the added index,
> the aggregate data array is VxDxC which you can get
> with cat:
>
> PDL> $VAR= cat($var1,$var2,$var3,$var4)->mv(-1,0)
> PDL> help 'vars'
> PDL variables in package main::
>
> Name Type Dimension Flow State Mem
> ----------------------------------------------------------------
> $VAR Double D [4,3,2] -C 0.00Kb
> $var1 Double D [3,2] P 0.05Kb
> $var2 Double D [3,2] P 0.05Kb
> $var3 Double D [3,2] P 0.05Kb
> $var4 Double D [3,2] P 0.05Kb
>
> PDL> p $VAR
>
> [
> [
> [111 112 113 114]
> [121 122 123 124]
> [131 132 133 134]
> ]
> [
> [211 212 213 214]
> [221 222 223 224]
> [231 232 233 234]
> ]
> ]
>
> To access the values for $day and $cell, you can slice as
> $VAR(:,($day-1),($cell-1)) where the -1 is because you have
> to convert between 1 offset counting and 0 offset counting
> as used by PDL, Perl, and C.
>
> Cheers,
> Chris
>
> On 5/29/2010 10:33 AM, P Kishor wrote:
> > I have the several piddles that look like so (actually, I have seven
> > or eight such piddles)
> >
> > $var1 = [
> > # day1 day2 day3 .. day365/366
> > [111 121 131 ..] # cell1
> > [211 221 231 ..] # cell2
> > .. # a few hundred to 10s of 1000s cells
> > ]
> >
> > $var2 = [
> > # day1 day2 day3
> > [112 122 132 ..] # cell1
> > [212 222 232 ..] # cell2
> > ..
> > ]
> >
> > I want to create the following composite piddle
> >
> > $vc = [
> > # cell day var1 var2 .. var7
> > [ 1 1 111 112 ..]
> > [ 1 2 121 122 ..] #<<<
> > [ 1 3 131 132 ..]
> > ..
> > [ 1 365 13651 13652 ..]
> > # end of cell1
> > [ 2 1 211 212 ..]
> > [ 2 2 221 222 ..]
> > [ 2 3 231 232 ..]
> > ..
> > [ 2 365 23651 23652 ..]
> > # end of cell2
> > ]
> >
> > and then, I want to be able to get all the values for any given cell
> > and day combination. So, for cell = 1, day = 2, I want the row marked
> > with #<<< above.
> >
> > 1 2 121 122 ..
> >
> > My hope is to do something like so
> >
> > for my $cell (1 .. $ncells) {
> > for my $day (1 .. $ndays) {
> > do something with $cell, $day, $var1, $var2 ..
> > where $var1, $var2, etc. are for the specific $cell, $day combo
> >
>
> _______________________________________________
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>
So Chris's point was that you could simply use one of the indices to keep
track of your day and cell. What's more, you can probably write a nice
Inline::Pdlpp function to handle your 'do something with data' that you
mention in your original post. It might be a bit confusing if you've never
played around with PDL::PP before, but here's a prototype for how that might
look, to get you going. You can find more info on Inline::Pdlpp at
http://search.cpan.org/~chm/PDL-2.4.6/Basic/Gen/Inline/Pdlpp.pm, and you can
find more info on PDL::PP at http://pdl.perl.org/?docs=PP&title=PDL::PP. I
wish the docs were bit more beginner-friendly, but it's not my top priority
at the moment. Still, ask questions if you've got them and we'll be happy to
help.
-------------%<-------------
#!/usr/bin/perl
use strict;
use warnings;
use PDL;
use PDL::NiceSlice;
use Inline qw(Pdlpp);
# Build the array of data
my $var1 = pdl q[ 111 121 131 ; 211 221 231 ]
my $var2 = pdl q[ 112 122 132 ; 212 222 232 ]
my $var3 = pdl q[ 113 123 133 ; 213 223 233 ]
my $var4 = pdl q[ 114 124 134 ; 214 224 234 ]
my $data = cat($var1, $var2, $var3, $var4);
# At this point we would index $data by ($day, $cell, $var).
# So $data(1, 0, 2) would give the data for 2nd day,
# first cell, third variable. If you would prefer a different
# order, use mv, xchg, or reorder to move the indices about.
# Now simply call the hammer function, which is defined below.
my $results = $data->my_hammer;
# $results holds the intended results of you calculation.
# Now you just need to save the results, or print them,
# or plot them, or do whatever you do with the processed data.
__DATA__
__Pdlpp__
pp_def('my_hammer',
Pars => 'data(day, cell, var), [o] results(dimension list)',
Code => q{
// Quasi-C-code to analyze your data goes here
// see
http://search.cpan.org/~chm/PDL-2.4.6/Basic/Gen/Inline/Pdlpp.pm
// and http://pdl.perl.org/?docs=PP&title=PDL::PP
// for details
},
);
-------------%<-------------
Have fun!
David
--
Sent via my carrier pigeon.
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