NAME
PDL::Graphics::Prima::Limits  defining a few useful constants for setting axis limits
DESCRIPTION
You probably won't ever need to use this module explicitly, but you will likely use the constants defined here to manipulate axis autoscaling. This module defines the constants lm::Auto
and lm::Hold
. If the explanation below does not make sense, these constants are also discussed in PDL::Graphics::Prima::Axis, PDL::Graphics::Prima::Simple, and elsewhere.
 lm::Auto

When you set an axis's min or max to
lm::Auto
, you turn on min or max autoscaling:# Set the xmin to 5 for now... $plot>x>min(5); # Turn on autoscaling for xmin: $plot>x>min(lm::Auto);
 lm::Hold

DEPRECATION CANDIDATE. I am considering deprecating this limit in favor of a new limit, discussed below. If you use
lm::Hold
, please let me know so that I can take your concerns into consideration. It presently serves as a fairly simple shorthand that I have not actually used in any of my real code. It is easy to create the desired effect with simple code, and I have concocted a much more helpful meaning for this value, detailed under the next item,lm::NextTick
.This constant gives a shorthand for changing from autoscaling to nonautoscaling. For example, suppose you are building a plot from multiple data sets and want to autoscale based on the first few but not for the remaining. In that case you might say:
$plot>dataSets>{'data'} = ds::Pair($x, $y); $plot>y>minmax(lm::Hold, lm::Hold); $plot>dataSets>{'model'} = ds::Func(\&my_func);
You can achieve the same ends like so:
$plot>dataSets>{'data'} = ds::Pair($x, $y); $plot>y>minmax($plot>y>minmax); $plot>dataSets>{'model'} = ds::Func(\&my_func);
If you just wanted to set the min to hold, you could use
lm::Hold
like this:$plot>y>min(lm::Hold);
which is equivalent to:
$plot>y>min($plot>y>min);
Also note that the return value of
$plot>y
min> returns different things depending on whether you are using scalar or list context. (Yes, that's an Axis thing, not a Limits thing, but it bears repeating here anyway.)  lm::NextTick

PROPOSAL CANDIDATE. I am considering adding this functionality some time in mid to late 2013. It would use the same bit representation as what is currently
lm::Hold
, so this would be a backwards incompatible change. However, I am not aware of any code that actually useslm::Hold
apart from a few of my own example scripts (I don't use it in any of my production code), so I suspect it will be fine. (Or, perhaps I should actually make turning autoscaling on or off a separate axis method. Ah well, ideas, ideas. Feedback welcome.)The proposed behavior of
lm::NextTick
is similar to that oflm::Auto
in that the axis limits would be computed automatically from the data. The major difference is thatlm::NextTick
is that, having computed the "tight" automatic min and/or max, the algorithm would actually set the min and/or max to a value slightly lower and/or higher, corresponding to the value that the Tick calculator would pick for the next major tick value. The goal here would be better static figures without having to tweak the limits.For example, when I create a default diamond plot in a containing window of 400x400 pixels with inputs
$x = pdl(1.1, 18.2)
and$y = pdl(10, 20)
, the actual axis extrema are slightly wider thant the data's min and max and come to 0.84 and 18.5, in order to accomodate the width of the diamonds. I see three tick marks at 5, 10, and 15. Whenlm::NextTick
gets implemented, the extrema for that specification would be 0 and 20, showing tick marks at 0, 5, 10, 15, and 20.That, at least, is the proposed specification. I imagine this would get a lot more use than
lm::Hold
, especially since it's not even possible at the moment.
AUTHOR
David Mertens (dcmertens.perl@gmail.com)
ADDITIONAL MODULES
Here is the full list of modules in this distribution:
 PDL::Graphics::Prima

Defines the Plot widget for use in Prima applications
 PDL::Graphics::Prima::Axis

Specifies the behavior of axes (but not the scaling)
 PDL::Graphics::Prima::DataSet

Specifies the behavior of DataSets
 PDL::Graphics::Prima::Limits

Defines the lm:: namespace
 PDL::Graphics::Prima::Palette

Specifies a collection of different color palettes
 PDL::Graphics::Prima::PlotType

Defines the different ways to visualize your data
 PDL::Graphics::Prima::ReadLine

Encapsulates all interaction with the Term::ReadLine family of modules.
 PDL::Graphics::Prima::Scaling

Specifies different kinds of scaling, including linear and logarithmic
 PDL::Graphics::Prima::Simple

Defines a number of useful functions for generating simple and notsosimple plots
LICENSE AND COPYRIGHT
Unless otherwise stated, all contributions in code and documentation are copyright (c) their respective authors, all rights reserved.
Portions of this module's code are copyright (c) 2011 The Board of Trustees at the University of Illinois.
Portions of this module's code are copyright (c) 20112013 Northwestern University.
Portions of this module's code are copyright (c) 20132014 Dickinson College.
This module's documentation is copyright (c) 20112014 David Mertens.
This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.