Colorplot of 2D array matplotlib

Question

So, I thought this was going to be really simple, but I've been having a lot of difficult finding exactly what I'm looking for in a comprehensible example.

Basically I want to make phase plots, so assuming I have a 2d array, how can I get matplotlib to convert this to a plot that I can attach titles, axes, and legends (color bars) to.

I'm looking for an extremely simple bare bones solution that only uses what is required that will work with any 2D array.

I'm certain this is simple and I'm just being thick somehow, but I'm really having a lot of trouble with this.

I have been tooling with the examples, but they don't seem well suited to what I'm trying to do: I like the general appearance of this graph, I'd just like to be able to pass in a 2dArray and have this same result:

import numpy as np
import matplotlib as ml
import matplotlib.pyplot as plt

H = [[1,2,3,4][5,6,7,8][9,10,11,12][13,14,15,16]]

fig = plt.figure(figsize=(6, 3.2))

ax = fig.add_subplot(111)
ax.set_title('colorMap')
X,Y = np.meshgrid(xedges, yedges)
plt.pcolormesh(X, Y, H)
ax.set_aspect('equal')

cax = fig.add_axes([0.12, 0.1, 0.78, 0.8])
cax.get_xaxis().set_visible(False)
cax.get_yaxis().set_visible(False)
cax.patch.set_alpha(0)
cax.set_frame_on(False)
plt.colorbar(orientation='vertical')
plt.show()

click on the picture that looks like what you want, they include the code. — tacaswell
– tacaswell, Commented May 11, 2013 at 1:31

user185160 · Accepted Answer · 2023-01-11 20:15:32Z

66

Here is the simplest example that has the key lines of code:

import numpy as np 
import matplotlib.pyplot as plt

H = np.array([[1, 2, 3, 4],
          [5, 6, 7, 8],
          [9, 10, 11, 12],
          [13, 14, 15, 16]])

plt.imshow(H, interpolation='none')
plt.show()

EDIT: (1/2023) Still working with Python 3.9.13

edited Jan 11, 2023 at 20:15

answered Nov 14, 2017 at 0:46

user185160

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1 Comment

Sreeragh A R Over a year ago

In Python 3.4 I was getting a blurry image for the above code. I had to turn off interpolation. plt.imshow(H, interpolation='none')

dirn · Accepted Answer · 2016-02-06 18:36:27Z

62

I'm afraid your posted example is not working, since X and Y aren't defined. So instead of pcolormesh let's use imshow:

import numpy as np
import matplotlib.pyplot as plt

H = np.array([[1, 2, 3, 4],
              [5, 6, 7, 8],
              [9, 10, 11, 12],
              [13, 14, 15, 16]])  # added some commas and array creation code

fig = plt.figure(figsize=(6, 3.2))

ax = fig.add_subplot(111)
ax.set_title('colorMap')
plt.imshow(H)
ax.set_aspect('equal')

cax = fig.add_axes([0.12, 0.1, 0.78, 0.8])
cax.get_xaxis().set_visible(False)
cax.get_yaxis().set_visible(False)
cax.patch.set_alpha(0)
cax.set_frame_on(False)
plt.colorbar(orientation='vertical')
plt.show()

edited Feb 6, 2016 at 18:36

dirn

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answered May 11, 2013 at 1:29

heltonbiker

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1 Comment

heltonbiker Over a year ago

Please note that you'll get the array indexes in the axes legend. If your rows and columns have X and Y values, take a look at the extent parameter of imshow()

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