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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Path3DCollection from 3D scatter cannot set_color","articleBody":"### Bug report\r\n\r\n**Bug summary**\r\nThe `set_color` method on the `Path3DCollection` object, such as the one returned by 3D `scatter` plot, does not set the color. I am filing this as a new issue because\r\n* all [previous instances](3370) reported the issue as related to the [figure not being updated / redrawn](https://stackoverflow.com/a/8974087)\r\n* previous [reports date back more than 3 years](5598) and to version 1.3.1\r\n* the MWE here shows the issue is present even before the first display (`show` call) of the figure\r\n* this report describes some other anomalies related to `alpha` that might favorable to handle together\r\n\r\n**Code for reproduction**\r\n\r\n```python\r\n# Can we change color after plotting? NO, independently of the color format.\r\n# Note: in 2D set_color() works as expected.\r\nimport matplotlib.pyplot as plt\r\nfrom mpl_toolkits.mplot3d import Axes3D\r\nfig = plt.figure()\r\nax = fig.gca(projection = \"3d\")\r\nsc1 = ax.scatter([0,1], [0,1], [1,1], color = (1,0,0,1), depthshade = False)\r\nsc2 = ax.scatter([0,1], [0,1], [2,2], color = (1,0,0,1), alpha=0.3, depthshade = True)\r\nsc3 = ax.scatter([0,1], [0,1], [3,3], color = (1,0,0,1), alpha=1.0, depthshade = False)\r\nsc4 = ax.scatter([0,1], [0,1], [4,4], color = (1,0,0,0.3), alpha=1.0, depthshade = True)\r\nsc1.set_color('blue')\r\nsc2.set_color(['blue', 'blue'])\r\nsc3.set_color([(0,0,1), (0,0,1)])\r\nsc4.set_color([(0,0,1,1), (0,0,1,1)])\r\nsc1.changed()  # workaround https://stackoverflow.com/a/8974087 does not work here \r\nax.set_zticks([1,2,3,4])\r\nax.set_zticklabels(['\"blue\"', '[b,b]', 'RGB', 'RGBA'])\r\nfig.show()\r\n```\r\n\r\n**Actual outcome**\r\n![mpl3d_bug1](https://user-images.githubusercontent.com/19959788/50365738-32519d00-0576-11e9-9c86-e76b5f979d44.png)\r\n\r\nWhile all the scatter plots are expected to have blue color.\r\n\r\n**Related questions**\r\n\r\nIf the issue is coming from how `Axes3D.scatter` produces the `Path3DCollection`, it might be worthy to note the following on the color-related alpha channel.\r\n\r\nContext: Does depthshade work with alpha value?\r\n* NO, depthshade is negatively overridden if alpha is provided, in addition, channel A from RGBA colors is omitted.\r\n* Remark: Since I did not find any note on this alpha vs channel A interaction in the docs, my expectation was to display using the product of alpha and A. Remark holds for 2D as well.\r\n```python\r\nfig = plt.figure()\r\nax = fig.gca(projection = \"3d\")\r\nsc1 = ax.scatter([0,1], [0,1], [1,1], color = (1,0,0,1), depthshade = False)\r\nsc2 = ax.scatter([0,1], [0,1], [2,2], color = (1,0,0,1), alpha=0.3, depthshade = True)\r\nsc3 = ax.scatter([0,1], [0,1], [3,3], color = (1,0,0,1), alpha=1.0, depthshade = False)\r\nsc4 = ax.scatter([0,1], [0,1], [4,4], color = (1,0,0,0.3), alpha=1.0, depthshade = True)\r\nax.set_zticks([1,2,3,4])\r\nax.set_zticklabels(['A=N a=1', 'A=1 a=.3', 'A=1 a=1', 'A=.3 a=1'])\r\nfig.show()\r\n```\r\n![mpl3d_bug2](https://user-images.githubusercontent.com/19959788/50365749-3c739b80-0576-11e9-963f-d017b1d76485.png)\r\n\r\n\r\nQuestion: Can we change alpha after plotting?\r\n* YES, independently of how alpha was provided.\r\n* Note: `set_alpha()` must be called with single scalar, otherwise a `TypeError` exception is raised.\r\n* Note: it seems that both the scatter constructor and set_alpha writes alpha into the color code because of the following\r\n   * `set_alpha(None)` does not restore alpha to 1.0, but reverts the negative override on depthscale\r\n   * `set_alpha(1.0)` overrides the A channel of RGBA colors\r\n* Remark: the above behavior is inconsistent with line plotting for the following reasons:\r\n   * there, `set_alpha(None)` reverts only the explicitly provided alpha, not the A channel of RGBA colors\r\n   * there, `set_alpha(1.0)` does not overwrite the A channel of RGBA colors, but the minimum of the alpha and A is used, however I would prefer product over minimum.\r\n```python\r\nfig = plt.figure()\r\nax = fig.gca(projection = \"3d\")\r\nsc1 = ax.scatter([0,1], [0,1], [1,1], color = (1,0,0,1), alpha=0.3, depthshade = True)\r\nsc2 = ax.scatter([0,1], [0,1], [2,2], color = (1,0,0,1), alpha=0.3, depthshade = True)\r\nsc3 = ax.scatter([0,1], [0,1], [3,3], color = (1,0,0,0.3), depthshade = True)\r\nsc4 = ax.scatter([0,1], [0,1], [4,4], color = (1,0,0,0.3), depthshade = True)\r\nsc1.set_alpha(1.0)\r\nsc2.set_alpha(None)\r\nsc3.set_alpha(None)\r\nsc4.set_alpha(1.0)\r\nax.set_zticks([1,2,3,4])\r\nax.set_zticklabels(['a=.3-\u003e1', 'a=.3-\u003eN', 'A=.3-\u003eN', 'A=.3-\u003e1'])\r\nfig.show()\r\n```\r\n![mpl3d_bug3](https://user-images.githubusercontent.com/19959788/50365757-49908a80-0576-11e9-9fcb-b7676fb9e40b.png)\r\n\r\n\r\n**Matplotlib version**\r\n  * Operating system: Windows\r\n  * Matplotlib version: 3.0.2\r\n  * Matplotlib backend: both module://ipykernel.pylab.backend_inline and Qt5\r\n  * Python version: 3.6.7 |Anaconda custom (64-bit)| (default, Dec 10 2018, 20:35:02) [MSC v.1915 64 bit (AMD64)]\r\n\r\n","author":{"url":"https://github.com/stippingerm","@type":"Person","name":"stippingerm"},"datePublished":"2018-12-21T22:23:06.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/13035/matplotlib/issues/13035"}