PDL::Basic -- Basic utility functions for PDL
This module contains basic utility functions for creating and manipulating piddles. Most of these functions are simplified interfaces to the more flexible functions in the modules PDL::Primitive and PDL::Slices.
use PDL::Basic;
Fills a piddle with X index values
$x = xvals($somearray); $x = xvals([OPTIONAL TYPE],$nx,$ny,$nz...);
etc. see zeroes.
perldl> print xvals zeroes(5,10) [ [0 1 2 3 4] [0 1 2 3 4] [0 1 2 3 4] [0 1 2 3 4] [0 1 2 3 4] [0 1 2 3 4] [0 1 2 3 4] [0 1 2 3 4] [0 1 2 3 4] [0 1 2 3 4] ]
Fills a piddle with Y index values
$x = yvals($somearray); yvals(inplace($somearray)); $x = yvals([OPTIONAL TYPE],$nx,$ny,$nz...);
perldl> print yvals zeroes(5,10) [ [0 0 0 0 0] [1 1 1 1 1] [2 2 2 2 2] [3 3 3 3 3] [4 4 4 4 4] [5 5 5 5 5] [6 6 6 6 6] [7 7 7 7 7] [8 8 8 8 8] [9 9 9 9 9] ]
Fills a piddle with Z index values
$x = zvals($somearray); zvals(inplace($somearray)); $x = zvals([OPTIONAL TYPE],$nx,$ny,$nz...);
perldl> print zvals zeroes(3,4,2) [ [ [0 0 0] [0 0 0] [0 0 0] [0 0 0] ] [ [1 1 1] [1 1 1] [1 1 1] [1 1 1] ] ]
X axis values between endpoints (see xvals).
$a = zeroes(100,100); $x = $a->xlinvals(0.5,1.5); $y = $a->ylinvals(-2,-1); # calculate Z for X between 0.5 and 1.5 and # Y between -2 and -1. $z = f($x,$y);
xlinvals, ylinvals and zlinvals return a piddle with the same shape as their first argument and linearly scaled values between the two other arguments along the given axis.
xlinvals
ylinvals
zlinvals
Y axis values between endpoints (see yvals).
See xlinvals for more information.
Z axis values between endpoints (see zvals).
Create histogram of a piddle
$hist = hist($data,[$min,$max,$step]); ($xvals,$hist) = hist($data,[$min,$max,$step]);
If requested, $xvals gives the computed bin centres
$xvals
A nice idiom (with PDL::Graphics::PGPLOT) is
bin hist $data; # Plot histogram
perldl> p $y [13 10 13 10 9 13 9 12 11 10 10 13 7 6 8 10 11 7 12 9 11 11 12 6 12 7] perldl> $h = hist $y,0,20,1; # hist with step 1, min 0 and 20 bins perldl> p $h [0 0 0 0 0 0 2 3 1 3 5 4 4 4 0 0 0 0 0 0]
Create a weighted histogram of a piddle
$hist = whist($data, $wt, [$min,$max,$step]); ($xvals,$hist) = whist($data, $wt, [$min,$max,$step]);
If requested, $xvals gives the computed bin centres. $data and $wt should have the same dimensionality and extents.
$data
$wt
bin whist $data, $wt; # Plot histogram
perldl> p $y [13 10 13 10 9 13 9 12 11 10 10 13 7 6 8 10 11 7 12 9 11 11 12 6 12 7] perldl> $wt = grandom($y->nelem) perldl> $h = whist $y, $wt, 0, 20, 1 # hist with step 1, min 0 and 20 bins perldl> p $h [0 0 0 0 0 0 -0.49552342 1.7987439 0.39450696 4.0073722 -2.6255299 -2.5084501 2.6458365 4.1671676 0 0 0 0 0 0]
Create array filled with a sequence of values
$a = sequence($b); $a = sequence [OPTIONAL TYPE], @dims;
perldl> p sequence(10) [0 1 2 3 4 5 6 7 8 9] perldl> p sequence(3,4) [ [ 0 1 2] [ 3 4 5] [ 6 7 8] [ 9 10 11] ]
Fills a piddle with radial distance values from some centre.
$r = rvals $piddle,{OPTIONS}; $r = rvals [OPTIONAL TYPE],$nx,$ny,...{OPTIONS};
Options: Centre => [$x,$y,$z...] # Specify centre Center => [$x,$y.$z...] # synonym. Squared => 1 # return distance squared (i.e., don't take the square root)
perldl> print rvals long,7,7,{Centre=>[2,2]} [ [2 2 2 2 2 3 4] [2 1 1 1 2 3 4] [2 1 0 1 2 3 4] [2 1 1 1 2 3 4] [2 2 2 2 2 3 4] [3 3 3 3 3 4 5] [4 4 4 4 4 5 5] ]
For a more general metric, one can define, e.g.,
sub distance { my ($a,$centre,$f) = @_; my ($r) = $a->allaxisvals-$centre; $f->($r); } sub l1 { sumover(abs($_[0])); } sub euclid { use PDL::Math 'pow'; pow(sumover(pow($_[0],2)),0.5); } sub linfty { maximum(abs($_[0])); }
so now
distance($a, $centre, \&euclid);
will emulate rvals, while \&l1 and \&linfty will generate other well-known norms.
\&l1
\&linfty
Fills a piddle with index values on Nth dimension
$z = axisvals ($piddle, $nth);
This is the routine, for which xvals, yvals etc are mere shorthands. axisvals can be used to fill along any dimension.
axisvals
Note the 'from specification' style (see zeroes) is not available here, for obvious reasons.
Generates a piddle with index values
$z = allaxisvals ($piddle);
allaxisvals produces an array with axis values along each dimension, adding an extra dimension at the start.
allaxisvals
allaxisvals($piddle)->slice("($nth)") will produce the same result as axisvals($piddle,$nth) (although with extra work and not inplace).
allaxisvals($piddle)->slice("($nth)")
axisvals($piddle,$nth)
It's useful when all the values will be required, as in the example given of a generalized rvals.
transpose rows and columns.
$b = transpose($a); $b = ~$a;
Also bound to the ~ unary operator in PDL::Matrix.
~
perldl> $a = sequence(3,2) perldl> p $a [ [0 1 2] [3 4 5] ] perldl> p transpose( $a ) [ [0 3] [1 4] [2 5] ]
To install PDL, copy and paste the appropriate command in to your terminal.
cpanm
cpanm PDL
CPAN shell
perl -MCPAN -e shell install PDL
For more information on module installation, please visit the detailed CPAN module installation guide.