René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Missing filled contours when using contourf","articleBody":"I am trying to plot plot a function over a 2D domain using `contourf`. Unfortunately, my first attempt did not work out very well. There was a region in the plot that was unexpectedly not covered by any contours. For debugging purposes, I have reduced the problem to the smallest dataset that I could find that also reveals the issue with missing filled contours:\r\n\r\n```\r\nimport matplotlib.pyplot as plt\r\nimport numpy as np\r\n\r\nv = np.array([0, 1, 2, 3])\r\nx, y = np.meshgrid(v, v)\r\n\r\nz = np.array([[5.5e-14, 5.5e-14, 5.5e-14, 5.5e-14],\r\n              [2e-13, 2e-13, 2e-13, 2e-13],\r\n              [2.2e-13, 2.2e-13, 2.2e-13, 2.2e-13],\r\n              [0, 0,0, 0]])\r\nfig, ax = plt.subplots()\r\ncntr = ax.contourf(x, y, z)\r\nfig.colorbar(cntr, ax=ax)\r\nplt.show()\r\n```\r\n![figure_1](https://user-images.githubusercontent.com/6708379/42379774-1daa6568-812c-11e8-976c-89e94ca17911.png)\r\n\r\nas you can see there are missing contours from `y = 1.5` to approximately `y = 2.0`.\r\n\r\nAnother strange thing I observed: If I normalize the `z` matrix by multiplying by e.g. `1e14` before plotting it works fine.\r\n\r\n**Matplotlib version**\r\n\u003c!--Please specify your platform and versions of the relevant libraries you are using:--\u003e\r\n  * Operating system: Ubuntu 18.04\r\n  * Matplotlib version: 2.2.2 (Installed with `pip`)\r\n  * Matplotlib backend: TkAgg\r\n  * Python version: 3.6.1\r\n\r\nNote: This question was first asked on stackoverflow.com: [Missing filled contours when using contourf](https://stackoverflow.com/q/51210497/2173773)\r\n\r\n","author":{"url":"https://github.com/hakonhagland","@type":"Person","name":"hakonhagland"},"datePublished":"2018-07-06T12:58:23.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/11587/matplotlib/issues/11587"}