CODEWITHSUNDEEP
pythonmatplotlibheatmap
Luka Vlaskalic
Luka Vlaskalic

Reputation: 465

Creating Density/Heatmap Plot from Coordinates and Magnitude in Python

I have some data which is the number of readings at each point on a 5x10 grid, which is in the format of;

X = [1, 2, 3, 4,..., 5]
Y = [1, 1, 1, 1,...,10]
Z = [9,8,14,0,89,...,0]

I would like to plot this as a heatmap/density map from above, but all of the matplotlib graphs (incl. contourf) that I have found are requiring a 2D array for Z and I don't understand why.

EDIT;

I have now collected the actual coordinates that I want to plot which are not as regular as what I have above they are;

X = [8,7,7,7,8,8,8,9,9.5,9.5,9.5,11,11,11,10.5,
     10.5,10.5,10.5,9,9,8, 8,8,8,6.5,6.5,1,2.5,4.5,
     4.5,2,2,2,3,3,3,4,4.5,4.5,4.5,4.5,3.5,2.5,2.5,
     1,1,1,2,2,2]

Y = [5.5,7.5,8,9,9,8,7.5,6,6.5,8,9,9,8,6.5,5.5,
      5,3.5,2,2,1,2,3.5,5,1,1,2,4.5,4.5,4.5,4,3,
      2,1,1,2,3,4.5,3.5,2.5,1.5,1,5.5,5.5,6,7,8,9,
      9,8,7]

z = [286,257,75,38,785,3074,1878,1212,2501,1518,419,33,
     3343,1808,3233,5943,10511,3593,1086,139,565,61,61,
     189,155,105,120,225,682,416,30632,2035,165,6777,
     7223,465,2510,7128,2296,1659,1358,204,295,854,7838,
     122,5206,6516,221,282]

From what I understand you can't use floats in a np.array so I have tried to multiply all values by 10 so that they are all integers, but I am still running into some issues. Am I trying to do something that will not work?

Upvotes: 1

Views: 2517

Answers (1)

aaossa
aaossa

Reputation: 3852

They expect a 2D array because they use the "row" and "column" to set the position of the value. For example, if array[2, 3] = 5, then when x is 2 and y is 3, the heatmap will use the value 5.

So, let's try transforming your current data into a single array:

>>> array = np.empty((len(set(X)), len(set(Y))))
>>> for x, y, z in zip(X, Y, Z):
        array[x-1, y-1] = z

If X and Y are np.arrays, you could do this too (SO answer):

>>> array = np.empty((X.shape[0], Y.shape[0]))
>>> array[np.array(X) - 1, np.array(Y) - 1] = Z

And now just plot the array as you prefer:

>>> plt.imshow(array, cmap="hot", interpolation="nearest")
>>> plt.show()

enter image description here

Upvotes: 2

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