René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: TwoSlopeNorm behaves like CenteredNorm","articleBody":"### Bug summary\r\n\r\nThe behavior of TwoSlopeNorm has changed from [Colormap Normalization 3.4.0]( https://matplotlib.org/3.4.0/tutorials/colors/colormapnorms.html#twoslopenorm-different-mapping-on-either-side-of-a-center) to [Colormap Normalization 3.5.1]( https://matplotlib.org/stable/tutorials/colors/colormapnorms.html#twoslopenorm-different-mapping-on-either-side-of-a-center). See the colorbar being centered and no longer a continuous linear scale.\r\n\r\n\r\n### Code for reproduction\r\n\r\n```python\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\nimport matplotlib.colors as colors\r\nimport matplotlib.cbook as cbook\r\nfrom matplotlib import cm\r\n\r\ndem = cbook.get_sample_data('topobathy.npz', np_load=True)\r\ntopo = dem['topo']\r\nlongitude = dem['longitude']\r\nlatitude = dem['latitude']\r\n\r\nfig, ax = plt.subplots()\r\n# make a colormap that has land and ocean clearly delineated and of the\r\n# same length (256 + 256)\r\ncolors_undersea = plt.cm.terrain(np.linspace(0, 0.17, 256))\r\ncolors_land = plt.cm.terrain(np.linspace(0.25, 1, 256))\r\nall_colors = np.vstack((colors_undersea, colors_land))\r\nterrain_map = colors.LinearSegmentedColormap.from_list(\r\n    'terrain_map', all_colors)\r\n\r\n# make the norm:  Note the center is offset so that the land has more\r\n# dynamic range:\r\ndivnorm = colors.TwoSlopeNorm(vmin=-500., vcenter=0, vmax=4000)\r\n\r\npcm = ax.pcolormesh(longitude, latitude, topo, rasterized=True, norm=divnorm,\r\n                    cmap=terrain_map, shading='auto')\r\n# Simple geographic plot, set aspect ratio beecause distance between lines of\r\n# longitude depends on latitude.\r\nax.set_aspect(1 / np.cos(np.deg2rad(49)))\r\nax.set_title('TwoSlopeNorm(x)')\r\ncb = fig.colorbar(pcm, shrink=0.6)\r\ncb.set_ticks([-500, 0, 1000, 2000, 3000, 4000])\r\nplt.show()\r\n```\r\n\r\n\r\n### Actual outcome\r\n\r\n**In 3.5.1**  \r\n![image](https://user-images.githubusercontent.com/7512099/148927510-d4109e88-e055-40a7-8a0d-be3c0d63d9f8.png)\r\n\r\n\r\n### Expected outcome\r\n\r\n\r\n**In 3.4.0**  \r\n![image](https://user-images.githubusercontent.com/7512099/148927566-1ca4ba09-ecc2-4f60-8dcd-6a94b9224e89.png)\r\n\r\n\r\n### Additional information\r\n\r\n_No response_\r\n\r\n### Operating system\r\n\r\nAlpine (Windows Subsystem for Linux)\r\n\r\n### Matplotlib Version\r\n\r\n3.5.1\r\n\r\n### Matplotlib Backend\r\n\r\nagg\r\n\r\n### Python version\r\n\r\n3.8.10\r\n\r\n### Jupyter version\r\n\r\n3.2.5\r\n\r\n### Installation\r\n\r\npip","author":{"url":"https://github.com/MartenSkogh","@type":"Person","name":"MartenSkogh"},"datePublished":"2022-01-11T10:44:59.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":15},"url":"https://github.com/22197/matplotlib/issues/22197"}