#4529: Implement plots with logarithmic scale
-----------------------------------------+----------------------------------
Reporter: ronanpaixao | Owner: ronanpaixao
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.1
Component: graphics | Resolution:
Keywords: plot log scale | Work issues: convenience functions
Report Upstream: N/A | Reviewers: Karl-Dieter Crisman
Authors: Punarbasu Purkayastha | Merged in:
Dependencies: #12974 | Stopgaps:
-----------------------------------------+----------------------------------
Changes (by kcrisman):
* reviewer: => Karl-Dieter Crisman
Old description:
> Attached is a patch which introduces log scale to `Graphics()` class.
>
> Depends on #12974.
>
> Apply the following patches in the specified order. `SAGE_ROOT` is the
> directory where the sage installation is present.
> {{{
> cd SAGE_ROOT/devel/sage
> ../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
> attachment/ticket/12974/trac_12974-fix_graphics_attributes.patch
> ../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
> attachment/ticket/12974/trac_12974-refactor.patch
> ../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
> attachment/ticket/12974/trac_12974-reorder_some_arguments.patch
> ../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
> attachment/ticket/12974/trac_12974-whitespace_cleanup.patch
> ../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
> attachment/ticket/4529/trac_4529-add_logscale_to_Graphics.2.patch
> ../../sage -b
> }}}
>
> ----
> '''OLD DISCUSSION BELOW :)'''
>
> Currently plot() has no option to use logarithmic scales.
>
> One workaround is to use matplotlib directly, with its semilogy(),
> semilogx() and loglog() functions, but that wouldn't produce plots with
> the customisations implemented in sage.
> Another workaround is messing with the plot figure like:
>
> {{{
> #!python
> import pylab
> p=plot(x,marker='.')
> f=pylab.figure()
> f.gca().set_xscale('log')
> p.save(figure=f)
> }}}
>
> But that creates two problems:
>
> * The first problem is that the adaptive choosing of points just
> considers linear scale, so the points get too much spaced apart in the
> beginning of the plot and too close in the end.
> * The second problem relates to the axis, which, for the same reason,
> isn't located right.
>
> Also, this requires the user to know how to deal with figures, which is
> not directly exposed by sage.
>
> There are some possibilities to fix that:
> 1. Make plot() detect if the figure changes the scales and modify the
> adaptive algorithm and the axis codes accordingly
> 2. Create a kwarg to tell plot() to implement the scale-change
> internally
> 3. Create other functions to use loglog(), semilogx() and semilogy()
> 4. Many (or all) of the above together, since they aren't mutually
> exclusive
>
> From what I noticed, Mathematica implements the separate functions way,
> but it may be better to fix the issue in plot() itself and if the other
> functions are wanted, just make it so that they call plot() with the
> correct arguments
New description:
Attached is a patch which introduces log scale to `Graphics()` class.
Depends on #12974.
Apply [attachment:trac_4529-add_logscale_to_Graphics.2.patch] and a patch
to be determined.
OR
Apply the following patches in the specified order. `SAGE_ROOT` is the
directory where the sage installation is present.
{{{
cd SAGE_ROOT/devel/sage
../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
attachment/ticket/12974/trac_12974-fix_graphics_attributes.patch
../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
attachment/ticket/12974/trac_12974-refactor.patch
../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
attachment/ticket/12974/trac_12974-reorder_some_arguments.patch
../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
attachment/ticket/12974/trac_12974-whitespace_cleanup.patch
../../sage -hg qimport -P http://trac.sagemath.org/sage_trac/raw-
attachment/ticket/4529/trac_4529-add_logscale_to_Graphics.2.patch
../../sage -b
}}}
----
'''OLD DISCUSSION BELOW :)'''
Currently plot() has no option to use logarithmic scales.
One workaround is to use matplotlib directly, with its semilogy(),
semilogx() and loglog() functions, but that wouldn't produce plots with
the customisations implemented in sage.
Another workaround is messing with the plot figure like:
{{{
#!python
import pylab
p=plot(x,marker='.')
f=pylab.figure()
f.gca().set_xscale('log')
p.save(figure=f)
}}}
But that creates two problems:
* The first problem is that the adaptive choosing of points just
considers linear scale, so the points get too much spaced apart in the
beginning of the plot and too close in the end.
* The second problem relates to the axis, which, for the same reason,
isn't located right.
Also, this requires the user to know how to deal with figures, which is
not directly exposed by sage.
There are some possibilities to fix that:
1. Make plot() detect if the figure changes the scales and modify the
adaptive algorithm and the axis codes accordingly
2. Create a kwarg to tell plot() to implement the scale-change internally
3. Create other functions to use loglog(), semilogx() and semilogy()
4. Many (or all) of the above together, since they aren't mutually
exclusive
From what I noticed, Mathematica implements the separate functions way,
but it may be better to fix the issue in plot() itself and if the other
functions are wanted, just make it so that they call plot() with the
correct arguments
--
Comment:
Some comments:
* Shouldn't `base=2` raise an error when `scale='linear'` in your
example? Maybe the
{{{
if scale is None:
return ('linear', 'linear', 10, 10)
}}}
could return 'linear', 'linear', None, None?
* In `_matplotlib_tick_formatter`, should `base` and `scale` be next to
each other in the function definition? (This is a very minor critique, of
course.)
* Nice consolidation of the `ticklabels` business at the end of the
patch.
* Regardless of the outcome of the poll (on which you can vote), I think
one should add a lot more examples in the documentation for `show` for the
various options. Lots of them.
* What's going on with the `pr, i = '', 0` thing removed? I just don't
know what it had been doing - seems to have been dead code, but I always
get nervous when I have no idea what it ''used'' to do...
* kini says that the `[13:]` seems brittle if matplotlib's API changes;
would it be possible to remove the specific string `\\mathdefault`
instead?
* I wonder about the not setting of the spines outward when the axes
shouldn't cross. Here is an example which serves the point:
{{{
sage: G = plot(exp(x), (x,5,10))
sage: G.show(scale=('semilogy', 2))
}}}
I don't even think this is a very atypical example to arise in
practice. It should be documented somehow.
* It's fairly easy to have just one tick in a given direction, which
usually raises an error in normal plots but isn't raising an error for
yours. I'm not sure if one would want to raise an error like "Use a
different base so that you get at least two ticks!" or something.
But even with all of these comments, and waiting for the post-poll patch,
'''fantastic''' job on this. Someone had to come along to finally wrap
this for us, it's been requested zillions of times, and this is very worth
the effort, thank you so much.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4529#comment:39>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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