{
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n\n.. redirect-from:: /gallery/subplots_axes_and_figures/colorbar_placement\n\n# Placing colorbars\n\nColorbars indicate the quantitative extent of image data.  Placing in\na figure is non-trivial because room needs to be made for them.\n\n## Automatic placement of colorbars\n\nThe simplest case is just attaching a colorbar to each Axes.  Note in this\nexample that the colorbars steal some space from the parent Axes.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "import matplotlib.pyplot as plt\nimport numpy as np\n\n# Fixing random state for reproducibility\nnp.random.seed(19680801)\n\nfig, axs = plt.subplots(2, 2)\ncmaps = ['RdBu_r', 'viridis']\nfor col in range(2):\n    for row in range(2):\n        ax = axs[row, col]\n        pcm = ax.pcolormesh(np.random.random((20, 20)) * (col + 1),\n                            cmap=cmaps[col])\n        fig.colorbar(pcm, ax=ax)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "The first column has the same type of data in both rows, so it may be\ndesirable to have just one colorbar. We do this by passing `.Figure.colorbar`\na list of Axes with the *ax* kwarg.\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, axs = plt.subplots(2, 2)\ncmaps = ['RdBu_r', 'viridis']\nfor col in range(2):\n    for row in range(2):\n        ax = axs[row, col]\n        pcm = ax.pcolormesh(np.random.random((20, 20)) * (col + 1),\n                            cmap=cmaps[col])\n    fig.colorbar(pcm, ax=axs[:, col], shrink=0.6)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "The stolen space can lead to Axes in the same subplot layout\nbeing different sizes, which is often undesired if the the\nx-axis on each plot is meant to be comparable as in the following:\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, axs = plt.subplots(2, 1, figsize=(4, 5), sharex=True)\nX = np.random.randn(20, 20)\naxs[0].plot(np.sum(X, axis=0))\npcm = axs[1].pcolormesh(X)\nfig.colorbar(pcm, ax=axs[1], shrink=0.6)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "This is usually undesired, and can be worked around in various ways, e.g.\nadding a colorbar to the other Axes and then removing it.  However, the most\nstraightforward is to use `constrained layout <constrainedlayout_guide>`:\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, axs = plt.subplots(2, 1, figsize=(4, 5), sharex=True, layout='constrained')\naxs[0].plot(np.sum(X, axis=0))\npcm = axs[1].pcolormesh(X)\nfig.colorbar(pcm, ax=axs[1], shrink=0.6)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Relatively complicated colorbar layouts are possible using this\nparadigm.  Note that this example works far better with\n``layout='constrained'``\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, axs = plt.subplots(3, 3, layout='constrained')\nfor ax in axs.flat:\n    pcm = ax.pcolormesh(np.random.random((20, 20)))\n\nfig.colorbar(pcm, ax=axs[0, :2], shrink=0.6, location='bottom')\nfig.colorbar(pcm, ax=[axs[0, 2]], location='bottom')\nfig.colorbar(pcm, ax=axs[1:, :], location='right', shrink=0.6)\nfig.colorbar(pcm, ax=[axs[2, 1]], location='left')"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Adjusting the spacing between colorbars and parent Axes\n\nThe distance a colorbar is from the parent Axes can be adjusted with the\n*pad* keyword argument.  This is in units of fraction of the parent Axes\nwidth, and the default for a vertical Axes is 0.05 (or 0.15 for a horizontal\nAxes).\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, axs = plt.subplots(3, 1, layout='constrained', figsize=(5, 5))\nfor ax, pad in zip(axs, [0.025, 0.05, 0.1]):\n    pcm = ax.pcolormesh(np.random.randn(20, 20), cmap='viridis')\n    fig.colorbar(pcm, ax=ax, pad=pad, label=f'pad: {pad}')\nfig.suptitle(\"layout='constrained'\")"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Note that if you do not use constrained layout, the pad command makes the\nparent Axes shrink:\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, axs = plt.subplots(3, 1, figsize=(5, 5))\nfor ax, pad in zip(axs, [0.025, 0.05, 0.1]):\n    pcm = ax.pcolormesh(np.random.randn(20, 20), cmap='viridis')\n    fig.colorbar(pcm, ax=ax, pad=pad, label=f'pad: {pad}')\nfig.suptitle(\"No layout manager\")"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "## Manual placement of colorbars\n\nSometimes the automatic placement provided by ``colorbar`` does not\ngive the desired effect.  We can manually create an Axes and tell\n``colorbar`` to use that Axes by passing the Axes to the *cax* keyword\nargument.\n\n### Using ``inset_axes``\n\nWe can manually create any type of Axes for the colorbar to use, but an\n`.Axes.inset_axes` is useful because it is a child of the parent Axes and can\nbe positioned relative to the parent.  Here we add a colorbar centered near\nthe bottom of the parent Axes.\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, ax = plt.subplots(layout='constrained', figsize=(4, 4))\npcm = ax.pcolormesh(np.random.randn(20, 20), cmap='viridis')\nax.set_ylim([-4, 20])\ncax = ax.inset_axes([0.3, 0.07, 0.4, 0.04])\nfig.colorbar(pcm, cax=cax, orientation='horizontal')"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "`.Axes.inset_axes` can also specify its position in data coordinates\nusing the *transform* keyword argument if you want your Axes at a\ncertain data position on the graph:\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, ax = plt.subplots(layout='constrained', figsize=(4, 4))\npcm = ax.pcolormesh(np.random.randn(20, 20), cmap='viridis')\nax.set_ylim([-4, 20])\ncax = ax.inset_axes([7.5, -1.7, 5, 1.2], transform=ax.transData)\nfig.colorbar(pcm, cax=cax, orientation='horizontal')"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### Colorbars attached to fixed-aspect-ratio Axes\n\nPlacing colorbars for Axes with a fixed aspect ratio pose a particular\nchallenge as the parent Axes changes size depending on the data view.\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, axs = plt.subplots(2, 2,  layout='constrained')\ncmaps = ['RdBu_r', 'viridis']\nfor col in range(2):\n    for row in range(2):\n        ax = axs[row, col]\n        pcm = ax.pcolormesh(np.random.random((20, 20)) * (col + 1),\n                            cmap=cmaps[col])\n        if col == 0:\n            ax.set_aspect(2)\n        else:\n            ax.set_aspect(1/2)\n        if row == 1:\n            fig.colorbar(pcm, ax=ax, shrink=0.6)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "We solve this problem using `.Axes.inset_axes` to locate the Axes in \"axes\ncoordinates\" (see `transforms_tutorial`).  Note that if you zoom in on\nthe parent Axes, and thus change the shape of it, the colorbar will also\nchange position.\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, axs = plt.subplots(2, 2, layout='constrained')\ncmaps = ['RdBu_r', 'viridis']\nfor col in range(2):\n    for row in range(2):\n        ax = axs[row, col]\n        pcm = ax.pcolormesh(np.random.random((20, 20)) * (col + 1),\n                            cmap=cmaps[col])\n        if col == 0:\n            ax.set_aspect(2)\n        else:\n            ax.set_aspect(1/2)\n        if row == 1:\n            cax = ax.inset_axes([1.04, 0.2, 0.05, 0.6])\n            fig.colorbar(pcm, cax=cax)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        ".. seealso::\n\n `axes_grid` has methods for manually creating colorbar Axes as well:\n\n - `demo-colorbar-with-inset-locator`\n - `demo-colorbar-with-axes-divider`\n\n"
      ]
    }
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