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# Copyright (C) 1998 Tuomas J. Lukka.
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# All rights reserved, except redistribution
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# with PDL under the PDL License permitted.
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package PDL::Demos::General;
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PDL::Demos::Routines->import();
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Welcome to a short tour of PDL's capabilities.
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This tour shows some of the main selling points
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of PDL. However, because we want this script to
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run everywhere, some modules which require external
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modules for use are explicitly excluded, namely
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- PDL::Graphics::TriD (3D Graphics) [*]
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- PDL::Graphics::PGPLOT (PGPLOT graphics)
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- PDL::IO::FlexRaw (flexible raw input/output)
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[*]: this module has its separate demos in a subdirectory.
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Note that your own scripts must start with
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to work properly, so that you can simply say
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or you can just try some of the commands illustrated
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in the demos by just retyping them at the perldl
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$a = zeroes 5,5; # 5x5 matrix
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# Now, don't think that the number of dimensions is limited
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$m = zeroes(3,2,2); # 3x2x2 cube
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$a ++; # Operators like increment work..
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# xvals and yvals (yes, there is also zvals...)
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# give you piddles which give the coordinate value.
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# So you can do things like
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$b = $a + 0.1 * xvals($a) + 0.01 * yvals($a);
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# Arithmetic operations work:
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output ((sin $x),"\n");
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# You can also take slices:
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output $b->slice(":,2:3"); # rows 2 and 3
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output $b->slice("2:3,:"); # or columns 2 and 3
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output $b->diagonal(0,1),"\n"; # 0 and 1 are the dimensions
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# One of the really nifty features is that the
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# slices are actually references back to the original
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$diag = $b->diagonal(0,1);
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output "Now, guess what \$b looks like?\n";
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# Yes, it has changed:
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# Another example (we only modify elements 0,2 and 4 of
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$t = $b->slice("0:4:2"); $t += 50;
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# There are lots of useful functions in e.g. PDL::Primitive
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# and PDL::Slices - we can't show you all but here are some
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output $b->sum, "\n";
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output $b->sumover,"\n"; # Only over first dim.
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output $b->xchg(0,1);
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output $b->minimum,"\n"; # over first dim.
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# Here are some more advanced tricks for selecting
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# parts of 1-D vectors:
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$i = which(sin($a) > 0.5); # Indices of those sines > 0.5
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output $a->index($i),"\n";
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# and we can have the effect of the last command in one
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# go using 'where' instead of 'which' and 'index' as in
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output $a->where(sin($a) > 0.5),"\n";
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# and finally take the sin of these elements
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# (to show that these are indeed the correct ones)
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output sin($a->index($i)),"\n";
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We hope you enjoyed these demos illustrating some
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of the basic capabilities of PDL.
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We encourage you to play with these commands in
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the perldl shell and use its online help support
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to find out more about these and other commands and
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Just type 'help' to get started.
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Demos/General.pm
