CODEWITHSUNDEEP
pythonmatplotlib
janiezbedny
janiezbedny

Reputation: 11

Error creating heatmap. ValueError: The truth value of an array with more than one element is ambiguous

I try to create a heatmap using hist2d. I have (x,y) coordinates and z values with a probability of this points.

x = list(range(1920))
y = list(range(1080))
z = np.zeros((1920, 1080))

plt.hist2d(x,y, bins = 256, weights=z)

VisibleDeprecationWarning: Creating an ndarray from ragged nested sequences (which is a list-or-tuple of lists-or-tuples-or ndarrays with different lengths or shapes) is deprecated. If you meant to do this, you must specify 'dtype=object' when creating the ndarray
  return array(a, dtype, copy=False, order=order, subok=True)
Traceback (most recent call last):
  File "create_heatmap3.py", line 109, in <module>
    plt.hist2d(x,y, bins = 50, weights=z)
  File "/home/wojtek/_mgr/venv/lib/python3.7/site-packages/matplotlib/pyplot.py", line 2849, in hist2d
    **({"data": data} if data is not None else {}), **kwargs)
  File "/home/wojtek/_mgr/venv/lib/python3.7/site-packages/matplotlib/__init__.py", line 1352, in inner
    return func(ax, *map(sanitize_sequence, args), **kwargs)
  File "/home/wojtek/_mgr/venv/lib/python3.7/site-packages/matplotlib/axes/_axes.py", line 7073, in hist2d
    density=density, weights=weights)
  File "<__array_function__ internals>", line 6, in histogram2d
  File "/home/wojtek/_mgr/venv/lib/python3.7/site-packages/numpy/lib/twodim_base.py", line 713, in histogram2d
    hist, edges = histogramdd([x, y], bins, range, normed, weights, density)
  File "<__array_function__ internals>", line 6, in histogramdd
  File "/home/wojtek/_mgr/venv/lib/python3.7/site-packages/numpy/lib/histograms.py", line 1049, in histogramdd
    smin, smax = _get_outer_edges(sample[:,i], range[i])
  File "/home/wojtek/_mgr/venv/lib/python3.7/site-packages/numpy/lib/histograms.py", line 322, in _get_outer_edges
    if not (np.isfinite(first_edge) and np.isfinite(last_edge)):
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Upvotes: 1

Views: 130

Answers (1)

Mikael &#214;hman
Mikael &#214;hman

Reputation: 2375

You misunderstand what the hist2d plot does and what sort of input it expects. You don't get to construct the grid, that's what hist2d does. You should simply supply the datapoints w_i(x_i, y_i) that the histogram accumulates. Matplotlibs documentation:

weights array-like, shape (n, ), optional

An array of values w_i weighing each sample (x_i, y_i).

x = np.random.rand(10000) * 1920
y = np.random.rand(10000) * 1080
w = np.random.rand(10000)
plt.hist2d(x, y, weights=w)
plt.show()

Upvotes: 1

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