CODEWITHSUNDEEP
pythonmatrixmatplotlib
Βασιλης Ιωσηφιδης
Βασιλης Ιωσηφιδης

Reputation: 769

Matplotlib 4D data in a 2D array

I am trying to plot a 4D array using as 4th dimension the color. Here is a sample of my matrix:

[[ 4.216  0.     1.     0.   ]
 [ 5.36   0.     1.     0.   ]
 [ 5.374  0.     2.     0.   ]
 ..., 
 [ 0.294  0.     1.     0.   ]
 [ 0.314  0.     2.     0.   ]
 [ 0.304  0.     1.     0.   ]]

4th column only contains values 0, 1 and 2.

So when I try to plot it using this script:

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.scatter(data[:,0],data[:,1],data[:,2], c=data[:,3], cmap=plt.hot())
plt.show()

I am getting this error:

TypeError: can't multiply sequence by non-int of type 'float'

Upvotes: 1

Views: 833

Answers (1)

jez
jez

Reputation: 15349

This isn't a 4D array. It's a 2D array with 4 columns (the 2 dimensions could be referred to as "rows" and "columns"). But I see what you're trying to say—each row could be interpreted as describing a point in 4-dimensional space, with the fourth "dimension" being colour.

Two-dimensionality is actually the key to the problem. I suspect your data variable is a numpy.matrix rather than a vanilla numpy.array. A matrix is particular class of 2D-array that has various special properties, including the fact that a slice of it (for example, data[:, 0]) is still a 2-dimensional matrix object, whereas .scatter() expects each argument to be a 1-D array.

The fix is to say:

data = numpy.asarray(data)

to convert your data from a matrix to a normal array whose column slices will be 1-dimensional.

BTW: you probably meant to say cmap='hot'. The call to plt.hot() sets the default colormap (so your figure may look right, but there's a side effect) but it actually returns None.

Upvotes: 2

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