Python – matplotlib colorbar placement and size

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I'm using quadmesh to create a simple polar projection plot. Here's a minimal script which produces basically what I'm trying to do:

from __future__ import unicode_literals
import numpy as np
import matplotlib.pyplot as plt

def make_plot(data,fig,subplot):
    nphi,nt = data.shape
    phi_coords = np.linspace(0,np.pi*2,nphi+1) - np.pi/2.
    theta_coords = np.linspace(0,np.radians(35),nt+1)

    ax = fig.add_subplot(subplot,projection='polar')
    ax.set_thetagrids((45,90,135,180,225,270,315,360),(9,12,15,18,21,24,3,6))
    ax.set_rgrids(np.arange(10,35,10),fmt='%s\u00b0')  

    theta,phi = np.meshgrid(phi_coords,theta_coords)
    quadmesh = ax.pcolormesh(theta,phi,data)
    ax.grid(True)
    fig.colorbar(quadmesh,ax=ax)
    return fig,ax


a = np.zeros((360,71)) + np.arange(360)[:,None]
b = np.random.random((360,71))
fig = plt.figure()
t1 = make_plot(a,fig,121)
t2 = make_plot(b,fig,122)
fig.savefig('test.png')

The above script creates a plot which looks like this:

enter image description here

I would like the colorbars to:

Not overlap the 6 label.
be scaled such that they are approximately the same height as the plot.

Is there any trick to make this work properly? (Note that this layout isn't the only one I will be using — e.g. I might use a 1×2 layout, or a 4×4 layout … It seems like there should be some way to scale the colorbar to the same height as the associated plot…)

Best Answer

This combination (and values near to these) seems to "magically" work for me to keep the colorbar scaled to the plot, no matter what size the display.

plt.colorbar(im,fraction=0.046, pad=0.04)

Related Solutions

Python – Difference between staticmethod and classmethod

Maybe a bit of example code will help: Notice the difference in the call signatures of foo, class_foo and static_foo:

class A(object):
    def foo(self, x):
        print(f"executing foo({self}, {x})")

    @classmethod
    def class_foo(cls, x):
        print(f"executing class_foo({cls}, {x})")

    @staticmethod
    def static_foo(x):
        print(f"executing static_foo({x})")

a = A()

Below is the usual way an object instance calls a method. The object instance, a, is implicitly passed as the first argument.

a.foo(1)
# executing foo(<__main__.A object at 0xb7dbef0c>, 1)

With classmethods, the class of the object instance is implicitly passed as the first argument instead of self.

a.class_foo(1)
# executing class_foo(<class '__main__.A'>, 1)

You can also call class_foo using the class. In fact, if you define something to be a classmethod, it is probably because you intend to call it from the class rather than from a class instance. A.foo(1) would have raised a TypeError, but A.class_foo(1) works just fine:

A.class_foo(1)
# executing class_foo(<class '__main__.A'>, 1)

One use people have found for class methods is to create inheritable alternative constructors.

With staticmethods, neither self (the object instance) nor cls (the class) is implicitly passed as the first argument. They behave like plain functions except that you can call them from an instance or the class:

a.static_foo(1)
# executing static_foo(1)

A.static_foo('hi')
# executing static_foo(hi)

Staticmethods are used to group functions which have some logical connection with a class to the class.

foo is just a function, but when you call a.foo you don't just get the function, you get a "partially applied" version of the function with the object instance a bound as the first argument to the function. foo expects 2 arguments, while a.foo only expects 1 argument.

a is bound to foo. That is what is meant by the term "bound" below:

print(a.foo)
# <bound method A.foo of <__main__.A object at 0xb7d52f0c>>

With a.class_foo, a is not bound to class_foo, rather the class A is bound to class_foo.

print(a.class_foo)
# <bound method type.class_foo of <class '__main__.A'>>

Here, with a staticmethod, even though it is a method, a.static_foo just returns a good 'ole function with no arguments bound. static_foo expects 1 argument, and a.static_foo expects 1 argument too.

print(a.static_foo)
# <function static_foo at 0xb7d479cc>

And of course the same thing happens when you call static_foo with the class A instead.

print(A.static_foo)
# <function static_foo at 0xb7d479cc>

Python – How to change the size of figures drawn with Matplotlib

figure tells you the call signature:

from matplotlib.pyplot import figure

figure(figsize=(8, 6), dpi=80)

figure(figsize=(1,1)) would create an inch-by-inch image, which would be 80-by-80 pixels unless you also give a different dpi argument.

Best Answer

Related Solutions

Python – Difference between staticmethod and classmethod

Python – How to change the size of figures drawn with Matplotlib

Related Topic