I am testing plotting a colored mesh based on two arrays. To do this, I first count the values for the first half of the grid, then for the second. I get two arrays and save them to a file. Also I am storing arrays with coordinates.
k1s1 = np.linspace(-1.0, 1.0, 11)
k2s1 = np.linspace(-1.0, 0.0, 11)
grid1 = np.zeros([len(k1s), len(k2s)])
for i, k1 in enumerate(k1s1):
for j, k2 in enumerate(k2s1):
grid1[i][j] = 1
with open('/content/drive/My Drive/Colab Notebooks/arraytest1.txt', 'w') as f:
np.savetxt(f, grid1)
k2s2 = np.linspace(0.0, 1.0, 11)
grid2 = np.zeros([len(k1s1), len(k2s2)])
for i, k1 in enumerate(k1s1):
for j, k2 in enumerate(k2s2):
grid2[i][j] = 2
with open('/content/drive/My Drive/Colab Notebooks/arraytest2.txt', 'w') as f:
np.savetxt(f, grid2)
with open('/content/drive/My Drive/Colab Notebooks/k1s1.txt', 'w') as f:
np.savetxt(f, k1s1)
with open('/content/drive/My Drive/Colab Notebooks/k2s1.txt', 'w') as f:
np.savetxt(f, k2s1)
with open('/content/drive/My Drive/Colab Notebooks/k2s2.txt', 'w') as f:
np.savetxt(f, k2s2)
Then I extract these arrays from the files and concatenate them.
with open('/content/drive/My Drive/Colab Notebooks/arraytest1.txt', 'r') as f:
grid1 = np.loadtxt(f)
with open('/content/drive/My Drive/Colab Notebooks/arraytest2.txt', 'r') as f:
grid2 = np.loadtxt(f)
with open('/content/drive/My Drive/Colab Notebooks/k1s1.txt', 'r') as f:
k1s1n = np.loadtxt(f)
with open('/content/drive/My Drive/Colab Notebooks/k2s1.txt', 'r') as f:
k2s1n = np.loadtxt(f)
with open('/content/drive/My Drive/Colab Notebooks/k2s2.txt', 'r') as f:
k2s2n = np.loadtxt(f)
grid3 = np.append(grid1, grid2)
k1s3 = k1s1n
k2s3 = np.append(k2s1n, k2s2n)
Then I try to build a color grid using the resulting arrays.
plt.pcolormesh(k1s3, k2s3, grid3, cmap=plt.cm.get_cmap('jet'))
plt.axes().set_aspect('equal', adjustable='box')
plt.colorbar()
And on the line
plt.pcolormesh(k1s3, k2s3, grid3, cmap=plt.cm.get_cmap('jet'))
an error like this appears:
Traceback (most recent call last)
<ipython-input-44-76ec1e216ce3> in <module>()
----> 1 plt.pcolormesh(k1s3, k2s3, grid3, cmap=plt.cm.get_cmap('jet'))
2 plt.axes().set_aspect('equal', adjustable='box')
3 plt.colorbar()
3 frames
/usr/local/lib/python3.7/dist-packages/matplotlib/pyplot.py in pcolormesh(alpha, norm, cmap, vmin, vmax, shading, antialiased, data, *args, **kwargs)
2723 *args, alpha=alpha, norm=norm, cmap=cmap, vmin=vmin,
2724 vmax=vmax, shading=shading, antialiased=antialiased,
-> 2725 **({"data": data} if data is not None else {}), **kwargs)
2726 sci(__ret)
2727 return __ret
/usr/local/lib/python3.7/dist-packages/matplotlib/__init__.py in inner(ax, data, *args, **kwargs)
1563 def inner(ax, *args, data=None, **kwargs):
1564 if data is None:
-> 1565 return func(ax, *map(sanitize_sequence, args), **kwargs)
1566
1567 bound = new_sig.bind(ax, *args, **kwargs)
/usr/local/lib/python3.7/dist-packages/matplotlib/axes/_axes.py in pcolormesh(self, alpha, norm, cmap, vmin, vmax, shading, antialiased, *args, **kwargs)
6102 allmatch = (shading == 'gouraud')
6103
-> 6104 X, Y, C = self._pcolorargs('pcolormesh', *args, allmatch=allmatch)
6105 Ny, Nx = X.shape
6106 X = X.ravel()
/usr/local/lib/python3.7/dist-packages/matplotlib/axes/_axes.py in _pcolorargs(funcname, allmatch, *args)
5678 if isinstance(Y, np.ma.core.MaskedArray):
5679 Y = Y.data
-> 5680 nrows, ncols = C.shape
5681 else:
5682 raise TypeError(
ValueError: not enough values to unpack (expected 2, got 1)
Though I checked all dimensions of all arrays. Please tell me why this can be and how to fix it?
Ok, I found the problem and solved it.
When I connected the 2D arrays grid1 and grid2 using the np.append() function, one array would be appended to the end of the other, resulting in a large ONE-DIMENSIONAL array.
In order to get one TWO DIMENSIONAL array after concatenation, you need to use np.concatenate().