René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Errorbar semilogy switch to log y removed error bars when crosses into negative","articleBody":"\u003c!--To help us understand and resolve your issue, please fill out the form to the best of your ability.--\u003e\r\n\u003c!--You can feel free to delete the sections that do not apply.--\u003e\r\n\r\n### Bug report\r\n\r\n**Bug summary**\r\n\r\nWhen plotting error bars on data points, where the data is positive but the bar with the data-error is entering negative values, switching to log Y axes using  semilogy() means that some data points are plotted without error bars at all (both y-err bars disappear).\r\n\r\n\u003c!--A short 1-2 sentences that succinctly describes the bug--\u003e\r\n\r\n**Code for reproduction**\r\n\r\ncreate a file example.dat:\r\n   x               dx                 y              dy\r\n1.046850 0.0029168 0.042551 0.02420 \r\n1.506679 0.0030152 0.027573 0.02252 \r\n3.028597 0.1959554 0.021218 0.00974 \r\n3.656348 0.1034119 0.002788 0.01059 \r\n4.949535 0.4693247 0.006276 0.00969 \r\n\r\nfrom astropy.io import ascii\r\nfrom pylab import figure, errorbar,semilogy\r\nt = ascii.read('example.dat')\r\nfigure()\r\nerrorbar(t['x'],t['y'],xerr=t['dx'],yerr=t['dy'],fmt='s')\r\n\r\nThis shows a linear plot with errorbars fine. The third data point error bar extends into negative territory.\r\n\r\nsemilogy()\r\n\r\nNow the plot has a log y axis, but the error bar of the third point is gone.\r\n\r\n\r\n\u003c!--A minimum code snippet required to reproduce the bug, also minimizing the number of dependencies required--\u003e\r\n\r\n```python\r\n# Paste your code here\r\n#\r\n#\r\n```\r\nfrom astropy.io import ascii\r\nfrom pylab import figure, errorbar,semilogy\r\nt = ascii.read('example.dat')\r\nfigure()\r\nerrorbar(t['x'],t['y'],xerr=t['dx'],yerr=t['dy'],fmt='s')\r\n\r\n#This shows a linear plot with errorbars fine. The third data point error bar extends into negative territory.\r\n\r\nsemilogy()\r\n\r\n#Now the plot has a log y axis, but the error bar of the third point is gone.\r\n**Actual outcome**\r\n\r\n\u003c!--The output produced by the above code, which may be a screenshot, console output, etc.--\u003e\r\n\u003cimg width=\"642\" alt=\"screen shot 2017-09-01 at 15 43 50\" src=\"https://user-images.githubusercontent.com/5159688/29974969-96166f08-8f2c-11e7-860d-b0359bc89a5d.png\"\u003e\r\n\u003cimg width=\"638\" alt=\"screen shot 2017-09-01 at 15 44 05\" src=\"https://user-images.githubusercontent.com/5159688/29974980-9b15bee6-8f2c-11e7-9da1-0148a620886b.png\"\u003e\r\n\r\n```\r\n# If applicable, paste the console output here\r\n#\r\n#\r\n```\r\n\r\n**Expected outcome**\r\n\r\nAn errorbar in the log plot, surely the positive bar, and the negative going a few (3 or 5) decades down (perhaps with an arrow ending).\r\n\r\n\u003c!--A description of the expected outcome from the code snippet--\u003e\r\n\u003c!--If this used to work in an earlier version of Matplotlib, please note the version it used to work on--\u003e\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: OSX\r\n  * Matplotlib Version: 2.0.2\r\n  * Python Version:2.7\r\n  * Jupyter Version (if applicable):\r\n  * Other Libraries: astropy\r\n\r\n\u003c!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--\u003e\r\n\u003c!--If you installed from conda, please specify which channel you used if not the default--\u003e\r\nanaconda astroconda\r\n","author":{"url":"https://github.com/PaulKuin","@type":"Person","name":"PaulKuin"},"datePublished":"2017-09-01T14:50:30.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/9149/matplotlib/issues/9149"}