Heatmap for given areas by coordinates-CodePudding

Let's say there is a 100*100 grid in the range of [0,1]. Each point in this grid with coordinates (x,y) has some value Z, where x and y can take any of the values {0.01, 0.02, 0.03, …, 1}. However, in the chart below, only points in certain areas matter (e.g. the rectangles in chart below).

I have a method F that when given a point with its coordinates tells me whether that point matters, I used a rectangle in the chart below just for demonstration - it’s not necessarily a rectangle. So I can calculate the centers of all the points for which I need the heatmap for - the rest should be white.

I was thinking maybe I can first build a 2D array of size 100*100 and populate it with the corresponding Z value for that coordinate, but then using the method F, set the Z for coordinates outside of those rectangles to some number (0, or -10000) that will result in white in the final heatmap, but couldn't quite make it happen.

Any help would be appreciated.

CodePudding user response：

If all you are trying to do is blank out some of the image, just set it to NaN:

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
data = np.random.randn(100, 100)
x = np.arange(100)
y = np.arange(100)
X, Y = np.meshgrid(x,y)

data[((X**2   (Y-30)**2) > 25**2)
     & ~((X>20) & (X<83) & (Y>60) & (Y<85))] = np.NaN

ax.imshow(data)

imshow has an extent argument that you can use to arbitrarily place images on the axes.

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
ax.imshow(np.random.randn(4, 5), extent=(3, 8, 2, 6))
ax.imshow(np.random.randn(7, 3), extent=(1, 2.7, 6.3, 9.8))
ax.set_xlim(0, 10)
ax.set_ylim(0, 10)
plt.show()

You can do the same thing with pcolormesh.