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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"plt.pcolormesh shape mismatch when shading='gouraud'","articleBody":"### Bug report\r\n\r\n**Bug summary**\r\n\r\nWhen running `plt.pcolormesh(X, Y, C, shading='flat')`, if `C.shape == (nrows, ncols)`, then if `X` and `Y` are 2-D arrays, their shapes must be either `(nrows, ncols)` or `(nrows+1, ncols+1)`.  If `shading='gouraud'`, however, the latter results in an error.  The code snippet below uses 1-D arrays for `X` and `Y`, but the same error occurs when they are the equivalent 2-D arrays.\r\n\r\n**Code for reproduction**\r\n\r\n\r\n```python\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\nx = np.arange(-4, 5)\r\ny = np.arange(-6, 7)\r\nxe = np.linspace(-4.5, 4.5, 10)\r\nye = np.linspace(-6.5, 6.5, 14)\r\nc = np.exp(-0.5*0.125*(x.reshape(1, -1)**2 + y.reshape(-1, 1)**2))\r\nplt.pcolormesh(xe, ye, c, shading='flat')  # works\r\nplt.pcolormesh(x, y, c, shading='gouraud')  # works\r\nplt.pcolormesh(xe, ye, c, shading='gouraud')  # doesn't work\r\n```\r\n\r\n**Actual outcome**\r\n\r\n```\r\nTraceback (most recent call last):\r\n\r\n  File \"\u003cipython-input-67-154f761638cd\u003e\", line 1, in \u003cmodule\u003e\r\n    plt.pcolormesh(xe, ye, c, shading='gouraud')\r\n\r\n  File \"/home/egranstedt/anaconda3/lib/python3.6/site-packages/matplotlib/pyplot.py\", line 3245, in pcolormesh\r\n    ret = ax.pcolormesh(*args, **kwargs)\r\n\r\n  File \"/home/egranstedt/anaconda3/lib/python3.6/site-packages/matplotlib/__init__.py\", line 1892, in inner\r\n    return func(ax, *args, **kwargs)\r\n\r\n  File \"/home/egranstedt/anaconda3/lib/python3.6/site-packages/matplotlib/axes/_axes.py\", line 5569, in pcolormesh\r\n    X, Y, C = self._pcolorargs('pcolormesh', *args, allmatch=allmatch)\r\n\r\n  File \"/home/egranstedt/anaconda3/lib/python3.6/site-packages/matplotlib/axes/_axes.py\", line 5187, in _pcolorargs\r\n    C.shape, Nx, Ny, funcname))\r\n\r\nTypeError: Dimensions of C (13, 9) are incompatible with X (10) and/or Y (14); see help(pcolormesh)\r\n```\r\n\r\n**Expected outcome**\r\n\r\nI expected `pcolormesh` would accept the same arrays for `X` and `Y  irrespective of the setting of the `shading` keyword argument.\r\n\r\n**Matplotlib version**\r\n\r\n- The error occurs with Matplotlib version 2.0.0 in the python 3.6 interpreter on Linux (installed via anaconda), but also seems to exist in older versions of Matplotlib (e.g., 1.5.1)\r\n\r\n","author":{"url":"https://github.com/egranstedt","@type":"Person","name":"egranstedt"},"datePublished":"2017-04-03T22:02:26.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":12},"url":"https://github.com/8422/matplotlib/issues/8422"}