René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Inconsistent behavior of markevery between semilogx and semilogy plots","articleBody":"### Bug report\r\n- The `markevery` option for `plot`, `semilogx`, `semilogy`, and `loglog` plotting methods has a weird difference of behavior between `plot / semilogy` and `semilogx / loglog`, when using `markevery = (float, float)`.\r\n\r\n**Code for reproduction**\r\n\r\n```python\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\n\r\n# Generate some data\r\nX = np.linspace(-10, 10, 1000)\r\nY = np.sin(X)**2\r\n\r\n# Specify markers\r\nmarkers = ['o', 'v', '^', '\u003c', '\u003e']\r\n\r\ndef markevery(i):\r\n    # I tried a *lot* of values here, none were working for the 4 plots\r\n    return (i / 50., 0.1)\r\n\r\nplt.figure()\r\n\r\n# First plot in normal plot\r\nplt.subplot(221)\r\nfor i in range(10):\r\n    plt.plot(X, Y + i / 10., marker=markers[i % len(markers)], markevery=markevery(i), label=str(i))\r\nplt.legend()\r\nplt.title(\"plt.plot(): markers are here!\")\r\n\r\n# Then plot in semilogx\r\nplt.subplot(222)\r\nfor i in range(10):\r\n    plt.semilogx(X, Y + i / 10., marker=markers[i % len(markers)], markevery=markevery(i), label=str(i))\r\nplt.legend()\r\nplt.title(\"plt.semilogx(): markers are NOT here!\")\r\n\r\n# And then semilogy\r\nplt.subplot(223)\r\nfor i in range(10):\r\n    plt.semilogy(X, Y + i / 10., marker=markers[i % len(markers)], markevery=markevery(i), label=str(i))\r\nplt.legend()\r\nplt.title(\"plt.semilogy(): markers are here!\")\r\n\r\n# Finally plot in loglog\r\nplt.subplot(224)\r\nfor i in range(10):\r\n    plt.loglog(X, Y + i / 10., marker=markers[i % len(markers)], markevery=markevery(i), label=str(i))\r\nplt.legend()\r\nplt.title(\"plt.loglog(): markers are NOT here!\")\r\n\r\nplt.suptitle(\"Weird behavior of markevery between plt.plot, plt.semilogx, plt.semilogy, plt.loglog\")\r\nplt.show()\r\n```\r\n\r\n**Actual outcome**\r\n![bug_markevery](https://cloud.githubusercontent.com/assets/11994719/24153472/d9d513de-0e4e-11e7-9655-347fe9d8ef8a.png)\r\n\r\n\r\n**Expected outcome**\r\n\r\n- One would expect the markers to be located in a **similar fashion** for each of the four plots method, `plot`, `semilogx`, `semilogy`, and `loglog`. The two plots on the left have markers correctly located (well spacen, with a different starting point for the different curves), and the two plots on the right do not show markers.\r\n- Note that I tried a lot of different values for the `markevery` parameters (here `markevery = (i / 50., 0.1)` for the various curves, with changing `i` to change the starting point of the markers),  and always encounter this inconsistency between left and right.\r\n\r\n**Matplotlib version**\r\n\r\n- Matplotlib version 2.0.0 (`2.0.0+3337.gc15694b`), with Python 3.5, on Ubuntu 16.10\r\n- Python installed with apt, latest version of Matplotlib installed with `pip --upgrade`.\r\n\r\n----\r\n\r\nMaybe I don't understand the [semantic behind using `markevery = (float, float)`](http://matplotlib.org/api/lines_api.html#matplotlib.lines.Line2D.set_markevery), but as far as I can tell, this behavior is weird.\r\nThanks in advance!\r\n","author":{"url":"https://github.com/Naereen","@type":"Person","name":"Naereen"},"datePublished":"2017-03-21T14:55:57.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":25},"url":"https://github.com/8356/matplotlib/issues/8356"}