René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Errorbars separated from markers with negative errors","articleBody":"### Bug summary\n\nIf unique upper and lower errors are specified, and one of them is negative, then the errorbar will appear separate from the marker. It looks like this was mentioned ages ago in #2717 but I could not find a follow up to that issue.\n\n### Code for reproduction\n\n```python\nimport matplotlib.pyplot as plt\r\n\r\n# 1\r\nplt.errorbar([0], [0], yerr=[[-0.5], [1]], marker=\"o\")\r\n\r\n# 2\r\nplt.errorbar([0], [0], xerr=[[-0.5], [1]], marker=\"o\")\r\n\r\n# 3\r\nplt.errorbar([0], [0], xerr=[[-0.5], [1]], yerr=[[-0.5], [1]], marker=\"o\")\n```\n\n\n### Actual outcome\n\n# 1\r\n\r\n![image](https://user-images.githubusercontent.com/7672534/133683908-e7b6f58d-67b7-46ae-a570-6a09ba1bbca8.png)\r\n\r\n# 2\r\n\r\n![image](https://user-images.githubusercontent.com/7672534/133683996-58793a04-0027-49ad-85d4-2213ceeea5bf.png)\r\n\r\n# 3\r\n\r\n![image](https://user-images.githubusercontent.com/7672534/133684029-f1bce9ec-f7b7-4fdf-aced-15f60262fdf7.png)\r\n\n\n### Expected outcome\n\nI understand the documentation states that the error inputs should be positive values, but I would expect some error like `ValueError` when there is a negative value provided, rather than it trying to make the plot. I would prefer an error being thrown and the plot not being made.\n\n### Operating system\n\nCentOS Linux release 7.9.2009 (Core)\n\n### Matplotlib Version\n\n3.4.3\n\n### Matplotlib Backend\n\nmodule://matplotlib_inline.backend_inline\n\n### Python version\n\n3.9.6\n\n### Jupyter version\n\n3.1.9\n\n### Other libraries\n\n_No response_\n\n### Installation\n\nconda\n\n### Conda channel\n\n_No response_","author":{"url":"https://github.com/nbrunett","@type":"Person","name":"nbrunett"},"datePublished":"2021-09-16T21:00:24.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/21101/matplotlib/issues/21101"}