René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Bivariate and multivariate colorbar","articleBody":"Project https://github.com/orgs/matplotlib/projects/9, which resolves github.com/matplotlib/matplotlib/issues/14168 is divided into a number of milestones, of which this is one (highlighted in bold).\n\n* Classes for bivariate and multivariate colormaps\n* `Colorizer` and `ColorizingArtist` to replace `ScalarMappable` and handle the norm→color pipeline\n* A `MultiNorm` class to handle the normalization of data for bivariate and multivariate colormaps\n* Ensure the `Colorizer` and `ColorizingArtist` work with `MultiNorm`, `BivarColormap` and `MultivarColormap`\n* Expose the new functionality via the top-level plotting functions: `imshow()`, `pcolor()` and `pcolormesh()`\n* **Create equivalents to `fig.colorbar()` for `BivarColormap` and `MultivarColormap` to work with `ColorizingArtist`**\n* Select bivariate and multivariate colormaps to include in matplotlib\n* Examples demonstrating the new functionality\n\n---\n\nThe following prototype uses a hypothetical function `fig.colorbar_2D(ColorizingArtist)` to display a `BivarColormap`:\n```py\nx = np.linspace(-1.5, 0.5, 200)\ny = np.linspace(-1, 1, 200)\nxx, yy = np.meshgrid(x, y)\nc = xx+1j*yy\nz = c\nfor i in range(7):\n    z = z**2+c\n\nfig, ax = plt.subplots(1, 1, figsize=(10, 6))\n\ncm = ax.pcolormesh(xx, yy, (z.imag, z.real), cmap='BiCone', vmin=-1, vmax=1)\nax.set_xlabel('Re{$c$}')\nax.set_ylabel('Im{$c$}')\nax.set_title('Mandelbrot $z_{7}$\\n $z_i = z_{i-1}^2+c$')\n\ncmap = fig.colorbar_2D(cm)\ncmap.set_ylabel('Im{$z$}')\ncmap.set_xlabel('Re{$z$}')\n\nfig.show()\n```\n\n\u003cimg width=\"1000\" height=\"600\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/d2fdf962-6647-4be1-9c3f-9752333c225f\" /\u003e\n\nWhile the name `colorbar_2D` is provisional, this functionality will be required as part of https://github.com/orgs/matplotlib/projects/9. \n\nMain questions include:\n* Function name\n* Should the function return an a new subclass of Axes? (subclass colorbar?) What members do the new class need?\n* Placement\n\nSimilar questions arise for the `MultivarColormap` class, i.e. in making the following plot:\n\n\u003cimg width=\"800\" height=\"800\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/0fcddaec-37f2-4691-8e3a-abc9b3368dcb\" /\u003e\n\n---\n\nNo work is expected on this issue until the milestones above it in https://github.com/orgs/matplotlib/projects/9 have been reached. ","author":{"url":"https://github.com/trygvrad","@type":"Person","name":"trygvrad"},"datePublished":"2025-09-08T12:38:26.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/30527/matplotlib/issues/30527"}