basic plotting: add support for setting the location and labels of all tick marks on the x and y axes

[williamstein]

Amazingly some very basic functionality for plotting hasn't yet been implemented! In particular, there is nothing yet for setting the location and labels of all tick marks on the x and y axes. This needs to be implemented.

Component: graphics

Author: Jason Grout, Karl-Dieter Crisman

Reviewer: Karl-Dieter Crisman

Merged: sage-4.6.alpha1

Issue created by migration from https://trac.sagemath.org/ticket/1431

[kcrisman]

comment:2

This should be available now with #5448, but this ticket would now be to expose that functionality from matplotlib.

[jasongrout]

comment:3

Attachment: formatter.patch.gz

Still needs doctest examples.

Example:

def multiple_of_pi(n,pos):
    m = n*1.0/float(pi)
    c=[i for i in convergents(m) if i.denominator()<12]
    q=c[-1]
    if q.denominator()==1:
        if q.numerator()==1:
            return r'$\pi$'
        elif q.numerator()==-1:
            return r'$-\pi$'            
        else:
            return r'$%s\pi$'%q
    else:
        if q.numerator()==1:
            return r'$\frac{\pi}{%s}$'%q.denominator()
        elif q.numerator()==-1:
            return r'$\frac{-\pi}{%s}$'%q.denominator()
        else:
            return r'$\frac{%s\pi}{%s}$'%(q.numerator(),q.denominator())

from matplotlib.ticker import MultipleLocator, FuncFormatter
plot(sin(x), (x, -4, 4), tick_locator=MultipleLocator(float(pi/3)), tick_formatter=FuncFormatter(multiple_of_pi))

[jasongrout]

Author: Jason Grout

[kcrisman]

comment:5

This looks like a great start. Now we need a wrapper to make creating the formatters and locators easy for the average user. I will try to help with that, and documentation, as I get a chance. Thanks!

[jasongrout]

comment:6

Personally, I think creating formatters and locators is easy. Notice what I did to create the locator: MultipleLocator(float(pi/3)). The formatter is slightly harder because it's a harder problem I was trying to solve---given a floating point number, find a nice multiple of pi expression for a label. In general, though, it's easy to just give a list of tick values and strings.

What did you have in mind for an easier wrapper?

[jasongrout]

comment:7

A simpler example:

def multiple_of_pi(n,pos):
    m = n*1.0/float(pi)
    c=[i for i in convergents(m) if i.denominator()<12]
    q=c[-1]
    return '$%s$'%latex(q*pi)

from matplotlib.ticker import MultipleLocator, FuncFormatter
plot(sin(x), (x, -4, 4), tick_locator=MultipleLocator(float(pi/4)), tick_formatter=FuncFormatter(multiple_of_pi))

[jasongrout]

comment:8

See #4529 for a related ticket---logarithmic scales.