René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Bar width expands between subsequent bars","articleBody":"### Bug report\r\n\r\n**Bug summary**\r\n\r\nIn an non-obvious fashion, sometimes bars get wrong width.  Specifically, each subsequent bar expands in width versus the prior one.  However, it does this for *some* datasets but not for others, with no pattern obvious to me.\r\n\r\n**Code for reproduction**\r\n\r\nSimplified from my actual code, but this demonstrates problem.\r\n\r\n```python\r\nprint(\"Matplotlib version:\", mpl.__version__)\r\nprint(\"\\nWomen:\\n\", women)\r\nprint(\"\\nMen:\\n\", men)\r\n\r\nattr = 'weight'\r\nfig, ax1 = plt.subplots()\r\nax2 = ax1.twinx() \r\nwidth = 9\r\nax2.bar(women[attr], women.total, width=0.75*width, alpha=0.15, label=\"Log Sales (W)\")\r\nax2.bar(men[attr], men.total, width=width, alpha=0.15, label=\"Log Sales (M)\")\r\nax2.grid(False)\r\nax2.set_yscale('log')\r\n```\r\n\r\nThe datasets are these:\r\n\r\n```\r\nWomen:\r\n     weight  return_rate    total\r\n0       90     0.163740     5240\r\n1      100     0.193345   197812\r\n2      110     0.180067   317877\r\n3      120     0.169454  1048820\r\n4      130     0.163293   760693\r\n5      140     0.157449  1294401\r\n6      150     0.154873   604145\r\n7      160     0.149343   800071\r\n8      170     0.147225   319150\r\n9      180     0.146417   465691\r\n10     190     0.146796   165134\r\n11     200     0.150957   195493\r\n\r\nMen:\r\n     weight  return_rate   total\r\n12      90     0.135135      37\r\n13     100     0.120954    3522\r\n14     110     0.117764    6547\r\n15     120     0.128846   41833\r\n16     130     0.103845   38750\r\n17     140     0.110603  134761\r\n18     150     0.107671   93628\r\n19     160     0.111633  215824\r\n20     170     0.112077  109800\r\n21     180     0.102720  231551\r\n22     190     0.104230   89821\r\n23     200     0.098818  132213\r\n```\r\n\r\n**Actual outcome**\r\n\r\nUnder Matplotlib 3.1.1 I get this distorted effect:\r\n\r\n![mpl-incorrect-bars-3 1](https://user-images.githubusercontent.com/2380665/65894166-49c87c80-e377-11e9-8551-33a47fc0fde6.png)\r\n\r\nIt appears that each subsequent bar is Nx wider.  I.e. first bar is fine, next is 2x width, next is 3x width, etc.\r\n\r\nEven stranger, the distortion applies only to the \"Men\" bars.  This is true if I change the order they are rendered in, and also is true if I comment out one or the other set of bars. I.e. women are fine, whether displayed solely or in combo; men are broken whether or not the women bars are displayed.\r\n\r\n**Expected outcome**\r\n\r\nUnder Matplotlib 3.0.3, the output looks as desired.  Specifically, the two sets of bars overlay each other with one narrower to aid reading both sets.\r\n\r\n![mpl-correct-bars-3 0](https://user-images.githubusercontent.com/2380665/65893884-c444cc80-e376-11e9-8c4e-0091afae2f9c.png)\r\n\r\n\r\n\r\n**Matplotlib version**\r\n  * Operating system: Linux popbmi 5.0.0-28-generic #30-Ubuntu SMP Wed Sep 4 11:47:46 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux\r\n  * Matplotlib version: 3.1.1\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): module://ipykernel.pylab.backend_inline\r\n  * Python version: '3.7.3 | packaged by conda-forge | (default, Jul  1 2019, 21:52:21) \\n[GCC 7.3.0]'\r\n  * Jupyter version (if applicable): 1.0.0\r\n  * Other libraries: \r\n\r\nConda installs. \r\n\r\n","author":{"url":"https://github.com/DavidMertz","@type":"Person","name":"DavidMertz"},"datePublished":"2019-09-30T15:51:19.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/15351/matplotlib/issues/15351"}