René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Colorbar for imshow messes interactive cursor with masked data","articleBody":"### Bug report\r\n\r\nAdding a colorbar when the mappable is the result of imshow for a masked array changes the behavior of the interactive z-data cursor and triggers a UserWarning.\r\n\r\n**Code for reproduction**\r\n```python\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\n\r\nmask = np.zeros((4, 4), bool)\r\nmask[:2] = True\r\nA = np.ma.array(np.random.rand(4, 4), mask=mask)\r\n\r\nfig, ax = plt.subplots(1, 1)\r\nim = ax.imshow(A)\r\nfig.colorbar(im)\r\n```\r\n\r\n**Actual outcome**\r\n```\r\n~/.anaconda3/lib/python3.7/site-packages/matplotlib/ticker.py:632: UserWarning: Warning: converting a masked element to nan.\r\n  return '%-12g' % value\r\n```\r\n![Screenshot from 2019-08-22 18-22-23](https://user-images.githubusercontent.com/52320542/63531938-e9d5ef00-c509-11e9-83ef-7ce9bc3f3c59.png)\r\n\r\n**Expected outcome**\r\nBefore adding the colorbar, the zdata cursor shows a blank (`[]`).\r\n\r\n**Matplotlib version**\r\n  * Operating system: Linux\r\n  * Matplotlib version: 3.1.1\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): Qt5Agg\r\n  * Python version: 3.7.3\r\n  * IPython version: 7.2.0\r\n  * Other libraries: \r\nMatplotlib installed from pip.\r\n\r\n\r\n\r\n","author":{"url":"https://github.com/Descanonge","@type":"Person","name":"Descanonge"},"datePublished":"2019-08-22T16:25:05.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/15103/matplotlib/issues/15103"}