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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"ScalarMappable should copy its input and allow non-arrays","articleBody":"\u003c!--\r\nWelcome! Thanks for thinking of a way to improve Matplotlib.\r\n\r\n\r\nBefore creating a new feature request please search the issues for relevant feature requests.\r\n--\u003e\r\n\r\n### Problem\r\n\r\nRecently I wanted to draw some colormapped vlines.  As LineCollection inherits from ScalarMappable, one can indeed write e.g.\r\n```python\r\nfrom pylab import *\r\nxs = vals = np.arange(10)\r\nplt.vlines(xs, 0, 1, array=vals)\r\nplt.show()\r\n```\r\nand get\r\n![test](https://user-images.githubusercontent.com/1322974/97629847-ff5c7800-1a2e-11eb-8905-e0fd43ffbd56.png)\r\n\r\nUnfortunately,\r\n1) The `array` kwarg only accepts ndarrays, and not e.g. nested lists: `plt.vlines(np.arange(10), 0, 1, array=[*range(10)])` crashes (at draw time, which is even worse) with \"AttributeError: 'list' object has no attribute 'ndim'\".  This is unlike most other Axes/pyplot APIs (e.g. `imshow`), which happily accept lists (nested/2D lists, for imshow).\r\n2) The `array` kwarg is not copied, so later changes to it get reflected back into the artist (i.e. doing `vals[5] = 45` *after* the call to `vlines` still affects the line colors).  Again, this is unlike other Axes/pyplot APIs (e.g. `imshow`), which insulate the artist from later changes to the input.\r\n\r\n### Proposed Solution\r\n\r\nMake a copy of the input and cast it to arrays.  (Well, modulo unit handling...)\r\n\r\n### Additional context and prior art\r\n\r\nBehave like `imshow`.","author":{"url":"https://github.com/anntzer","@type":"Person","name":"anntzer"},"datePublished":"2020-10-29T20:44:12.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/18841/matplotlib/issues/18841"}