René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: cannot give init value for RangeSlider widget","articleBody":"### Bug summary\r\n\r\nI think `xy[4] = .25, val[0]` should be commented in /matplotlib/widgets. py\", line 915, in set_val\r\nas it prevents to initialized value for RangeSlider\r\n\r\n### Code for reproduction\r\n\r\n```python\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\nfrom matplotlib.widgets import RangeSlider\r\n\r\n# generate a fake image\r\nnp.random.seed(19680801)\r\nN = 128\r\nimg = np.random.randn(N, N)\r\n\r\nfig, axs = plt.subplots(1, 2, figsize=(10, 5))\r\nfig.subplots_adjust(bottom=0.25)\r\n\r\nim = axs[0].imshow(img)\r\naxs[1].hist(img.flatten(), bins='auto')\r\naxs[1].set_title('Histogram of pixel intensities')\r\n\r\n# Create the RangeSlider\r\nslider_ax = fig.add_axes([0.20, 0.1, 0.60, 0.03])\r\nslider = RangeSlider(slider_ax, \"Threshold\", img.min(), img.max(),valinit=[0.0,0.0])\r\n\r\n# Create the Vertical lines on the histogram\r\nlower_limit_line = axs[1].axvline(slider.val[0], color='k')\r\nupper_limit_line = axs[1].axvline(slider.val[1], color='k')\r\n\r\n\r\ndef update(val):\r\n    # The val passed to a callback by the RangeSlider will\r\n    # be a tuple of (min, max)\r\n\r\n    # Update the image's colormap\r\n    im.norm.vmin = val[0]\r\n    im.norm.vmax = val[1]\r\n\r\n    # Update the position of the vertical lines\r\n    lower_limit_line.set_xdata([val[0], val[0]])\r\n    upper_limit_line.set_xdata([val[1], val[1]])\r\n\r\n    # Redraw the figure to ensure it updates\r\n    fig.canvas.draw_idle()\r\n\r\n\r\nslider.on_changed(update)\r\nplt.show()\r\n```\r\n\r\n\r\n### Actual outcome\r\n\r\n```python\r\n  File \"\u003cipython-input-52-b704c53e18d4\u003e\", line 19, in \u003cmodule\u003e\r\n    slider = RangeSlider(slider_ax, \"Threshold\", img.min(), img.max(),valinit=[0.0,0.0])\r\n\r\n  File \"/Users/Vincent/opt/anaconda3/envs/py38/lib/python3.8/site-packages/matplotlib/widgets.py\", line 778, in __init__\r\n    self.set_val(valinit)\r\n\r\n  File \"/Users/Vincent/opt/anaconda3/envs/py38/lib/python3.8/site-packages/matplotlib/widgets.py\", line 915, in set_val\r\n    xy[4] = val[0], .25\r\n\r\nIndexError: index 4 is out of bounds for axis 0 with size 4\r\n```\r\n\r\n### Expected outcome\r\n\r\nrange slider with user initial values\r\n\r\n### Additional information\r\n\r\nerror can be removed by commenting this line\r\n```python\r\n\r\n    def set_val(self, val):\r\n        \"\"\"\r\n        Set slider value to *val*.\r\n\r\n        Parameters\r\n        ----------\r\n        val : tuple or array-like of float\r\n        \"\"\"\r\n        val = np.sort(np.asanyarray(val))\r\n        if val.shape != (2,):\r\n            raise ValueError(\r\n                f\"val must have shape (2,) but has shape {val.shape}\"\r\n            )\r\n        val[0] = self._min_in_bounds(val[0])\r\n        val[1] = self._max_in_bounds(val[1])\r\n        xy = self.poly.xy\r\n        if self.orientation == \"vertical\":\r\n            xy[0] = .25, val[0]\r\n            xy[1] = .25, val[1]\r\n            xy[2] = .75, val[1]\r\n            xy[3] = .75, val[0]\r\n            # xy[4] = .25, val[0]\r\n        else:\r\n            xy[0] = val[0], .25\r\n            xy[1] = val[0], .75\r\n            xy[2] = val[1], .75\r\n            xy[3] = val[1], .25\r\n            # xy[4] = val[0], .25\r\n        self.poly.xy = xy\r\n        self.valtext.set_text(self._format(val))\r\n        if self.drawon:\r\n            self.ax.figure.canvas.draw_idle()\r\n        self.val = val\r\n        if self.eventson:\r\n            self._observers.process(\"changed\", val)\r\n\r\n```\r\n\r\n### Operating system\r\n\r\nOSX\r\n\r\n### Matplotlib Version\r\n\r\n3.5.1\r\n\r\n### Matplotlib Backend\r\n\r\n_No response_\r\n\r\n### Python version\r\n\r\n3.8\r\n\r\n### Jupyter version\r\n\r\n_No response_\r\n\r\n### Installation\r\n\r\npip","author":{"url":"https://github.com/vpicouet","@type":"Person","name":"vpicouet"},"datePublished":"2022-03-23T02:29:06.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":25},"url":"https://github.com/22686/matplotlib/issues/22686"}