René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: pcolor writing to read-only input mask","articleBody":"### Bug summary\r\n\r\nWhen the parameter `X` or `Y` is a masked array with a read-only mask, `pcolor` fails with `ValueError: array is read-only`\r\n\r\n### Code for reproduction\r\n\r\n```python\r\nimport matplotlib.pyplot as plt\r\nimport numpy as np\r\n\r\nx = np.linspace(0, 1, 10)\r\ny = np.linspace(0, 1, 10)\r\nX, Y = np.meshgrid(x, y)\r\nZ = np.sin(2 * np.pi * X) * np.cos(2 * np.pi * Y)\r\n\r\nmask = np.broadcast_to([True, False] * 5, Z.shape)\r\nmasked_X = np.ma.array(X, mask=mask)\r\nmasked_Y = np.ma.array(Y, mask=mask)\r\nmasked_Z = np.ma.array(Z, mask=mask)\r\n\r\nplt.pcolormesh(masked_X, masked_Y, masked_Z)\r\n```\r\n\r\n\r\n### Actual outcome\r\n\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"/Library/Python/3.9/lib/python/site-packages/matplotlib/pyplot.py\", line 2773, in pcolormesh\r\n    __ret = gca().pcolormesh(\r\n  File \"/Library/Python/3.9/lib/python/site-packages/matplotlib/__init__.py\", line 1442, in inner\r\n    return func(ax, *map(sanitize_sequence, args), **kwargs)\r\n  File \"/Library/Python/3.9/lib/python/site-packages/matplotlib/axes/_axes.py\", line 6220, in pcolormesh\r\n    X, Y, C, shading = self._pcolorargs('pcolormesh', *args,\r\n  File \"/Library/Python/3.9/lib/python/site-packages/matplotlib/axes/_axes.py\", line 5713, in _pcolorargs\r\n    X, Y = [cbook.safe_masked_invalid(a) for a in [X, Y]]\r\n  File \"/Library/Python/3.9/lib/python/site-packages/matplotlib/axes/_axes.py\", line 5713, in \u003clistcomp\u003e\r\n    X, Y = [cbook.safe_masked_invalid(a) for a in [X, Y]]\r\n  File \"/Library/Python/3.9/lib/python/site-packages/matplotlib/cbook/__init__.py\", line 715, in safe_masked_invalid\r\n    xm = np.ma.masked_invalid(x, copy=False)\r\n  File \"/Library/Python/3.9/lib/python/site-packages/numpy/ma/core.py\", line 2360, in masked_invalid\r\n    res = masked_where(~(np.isfinite(a)), a, copy=copy)\r\n  File \"/Library/Python/3.9/lib/python/site-packages/numpy/ma/core.py\", line 1942, in masked_where\r\n    result.mask = _shrink_mask(cond)\r\n  File \"/Library/Python/3.9/lib/python/site-packages/numpy/ma/core.py\", line 3516, in mask\r\n    self.__setmask__(value)\r\n  File \"/Library/Python/3.9/lib/python/site-packages/numpy/ma/core.py\", line 3462, in __setmask__\r\n    current_mask.flat = mask\r\nValueError: array is read-only\r\n\r\n\r\n### Expected outcome\r\n\r\nNo error\r\n\r\n### Additional information\r\n\r\nThe error still exists because I missed the following code in fixing #26093:\r\nhttps://github.com/matplotlib/matplotlib/blob/9fdf6adf70819c8d34e9f47eeb8470aea35d78c0/lib/matplotlib/axes/_axes.py#L5776-L5783\r\n\r\nAnd I will fix it as well if allowed.\r\n\r\n### Operating system\r\n\r\nOS/X\r\n\r\n### Matplotlib Version\r\n\r\n3.7.1\r\n\r\n### Matplotlib Backend\r\n\r\nMacOSX\r\n\r\n### Python version\r\n\r\n3.9\r\n\r\n### Jupyter version\r\n\r\n_No response_\r\n\r\n### Installation\r\n\r\nNone","author":{"url":"https://github.com/Rylie-W","@type":"Person","name":"Rylie-W"},"datePublished":"2023-07-01T11:31:54.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/26230/matplotlib/issues/26230"}