René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[ENH]: Ability to set imshow vmin/vmax with units ","articleBody":"### Problem\n\nTrying to use `imshow` with unit-ful data and setting vmin/vmax with units fails. It would be great if this was possible!\r\n\r\n\r\n```python\r\nimport matplotlib.pyplot as plt\r\nimport numpy as np\r\n\r\nimport pint\r\nureg = pint.UnitRegistry()\r\nureg.setup_matplotlib()\r\n\r\nX, Y = np.meshgrid(np.linspace(-3, 3, 16), np.linspace(-3, 3, 16))\r\nZ = (1 - X/2 + X**5 + Y**3) * np.exp(-X**2 - Y**2)\r\nZ *= ureg.kg\r\n\r\nfig, ax = plt.subplots()\r\nax.imshow(Z, vmin=1*ureg.kg, vmax=2*ureg.kg)\r\nplt.show()\r\n```\r\n\r\n```python\r\n% python test.py\r\n/Users/dstansby/github/matplotlib/lib/matplotlib/cbook.py:672: UnitStrippedWarning: The unit of the quantity is stripped when downcasting to ndarray.\r\n  x = np.array(x, subok=True, copy=copy)\r\n/Users/dstansby/github/matplotlib/lib/matplotlib/image.py:452: UnitStrippedWarning: The unit of the quantity is stripped when downcasting to ndarray.\r\n  dv = np.float64(self.norm.vmax) - np.float64(self.norm.vmin)\r\n/Users/dstansby/github/matplotlib/lib/matplotlib/image.py:453: UnitStrippedWarning: The unit of the quantity is stripped when downcasting to ndarray.\r\n  vmid = np.float64(self.norm.vmin) + dv / 2\r\n/Users/dstansby/github/matplotlib/lib/matplotlib/image.py:482: UnitStrippedWarning: The unit of the quantity is stripped when downcasting to ndarray.\r\n  vrange = np.array([vmin, vmax], dtype=scaled_dtype)\r\nTraceback (most recent call last):\r\n  File \"/Users/dstansby/mambaforge/envs/mpl/lib/python3.10/site-packages/pint/facets/plain/quantity.py\", line 707, in __float__\r\n    raise DimensionalityError(self._units, \"dimensionless\")\r\npint.errors.DimensionalityError: Cannot convert from 'kilogram' to 'dimensionless'\r\n\r\nThe above exception was the direct cause of the following exception:\r\n\r\nTraceback (most recent call last):\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/backend_bases.py\", line 1223, in _on_timer\r\n    ret = func(*args, **kwargs)\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/backends/backend_macosx.py\", line 68, in callback_func\r\n    callback()\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/backends/backend_macosx.py\", line 88, in _draw_idle\r\n    self.draw()\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/backends/backend_macosx.py\", line 50, in draw\r\n    super().draw()\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/backends/backend_agg.py\", line 400, in draw\r\n    self.figure.draw(self.renderer)\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/artist.py\", line 95, in draw_wrapper\r\n    result = draw(artist, renderer, *args, **kwargs)\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/artist.py\", line 72, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/figure.py\", line 3116, in draw\r\n    mimage._draw_list_compositing_images(\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/image.py\", line 131, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/artist.py\", line 72, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/axes/_base.py\", line 3066, in draw\r\n    mimage._draw_list_compositing_images(\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/image.py\", line 131, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/artist.py\", line 72, in draw_wrapper\r\n    return draw(artist, renderer)\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/image.py\", line 641, in draw\r\n    im, l, b, trans = self.make_image(\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/image.py\", line 948, in make_image\r\n    return self._make_image(self._A, bbox, transformed_bbox, clip,\r\n  File \"/Users/dstansby/github/matplotlib/lib/matplotlib/image.py\", line 482, in _make_image\r\n    vrange = np.array([vmin, vmax], dtype=scaled_dtype)\r\nValueError: setting an array element with a sequence.\r\n```\n\n### Proposed solution\n\n_No response_","author":{"url":"https://github.com/dstansby","@type":"Person","name":"dstansby"},"datePublished":"2023-01-23T16:19:13.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/25062/matplotlib/issues/25062"}