René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Unexpected behaviour in errorbar","articleBody":"I have some data y plotted against x with asymmetric error bars yerr (`=[up, down]`). The data, y, contains some `np.nan` values at the end and likewise for yerr. However, when I plot the data using matplotlib's `errorbar` function, it gets this weird marker behaviour:\n\n![See around 30 on x axis](http://i.stack.imgur.com/s1fNy.png)\n\nWhat could cause this? I ran a few checks  and the nan values line up, meaning that they shouldn't be plotted at all!\n\nHeres the function:\n\n`axis.errorbar(profile.R, profile.M, yerr=profile.MW, fmt='b.')`\n\n`axis.set_ylim(axis.get_ylim()[::-1])`\n\nand here's some pictures:\nafter re-phrase: `axis.errorbar(profile.R, profile.M, yerr=(profile.MW[0], profile.MW[1]), fmt='b.')`, it still produces the same plot\nafter re-phrasing to use only one set: \n\n`axis.errorbar(profile.R, profile.M, yerr=(profile.MW[1], profile.MW[1]), fmt='b.')`\n![Only with up errorbars](http://i.stack.imgur.com/CN6ic.png)\n\n(this also happens if I use `profile.MW[0]`)\n\nI've also downgraded matplotlib and it still doesn't work!\n\nBut when I take the values out of their np.arrays for the last 8 elements by copy and paste (`axis.errorbar([32.9592, 34.60716, 36.33696,  38.15418,  40.06254,  42.06576,  44.16756, 46.37724],[np.nan, 28.18328608, 27.41428602, np.nan, 27.30407038, np.nan, np.nan, np.nan], yerr=[[np.nan, 1.16532339, 0.73753135, np.nan, 0.68722997, np.nan, np.nan, np.nan], [np.nan, 1.16532339, 0.73753135, np.nan, 0.68722997, np.nan, np.nan, np.nan]])`)\n\n![WTF it works now?](http://i.stack.imgur.com/p6aZp.png)\nit works!! WTF!\n\nAny ideas?\n\nThanks\n","author":{"url":"https://github.com/lapsed-pacifist","@type":"Person","name":"lapsed-pacifist"},"datePublished":"2014-01-10T19:52:52.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/2717/matplotlib/issues/2717"}