.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "gallery/images_contours_and_fields/colormap_normalizations.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. meta:: :keywords: codex .. note:: :class: sphx-glr-download-link-note Click :ref:`here ` to download the full example code .. rst-class:: sphx-glr-example-title .. _sphx_glr_gallery_images_contours_and_fields_colormap_normalizations.py: ======================= Colormap Normalizations ======================= Demonstration of using norm to map colormaps onto data in non-linear ways. .. redirect-from:: /gallery/userdemo/colormap_normalizations .. GENERATED FROM PYTHON SOURCE LINES 10-15 .. code-block:: default import numpy as np import matplotlib.pyplot as plt import matplotlib.colors as colors .. GENERATED FROM PYTHON SOURCE LINES 16-18 Lognorm: Instead of pcolor log10(Z1) you can have colorbars that have the exponential labels using a norm. .. GENERATED FROM PYTHON SOURCE LINES 18-41 .. code-block:: default N = 100 X, Y = np.mgrid[-3:3:complex(0, N), -2:2:complex(0, N)] # A low hump with a spike coming out of the top. Needs to have # z/colour axis on a log scale so we see both hump and spike. linear # scale only shows the spike. Z1 = np.exp(-X**2 - Y**2) Z2 = np.exp(-(X * 10)**2 - (Y * 10)**2) Z = Z1 + 50 * Z2 fig, ax = plt.subplots(2, 1) pcm = ax[0].pcolor(X, Y, Z, norm=colors.LogNorm(vmin=Z.min(), vmax=Z.max()), cmap='PuBu_r', shading='nearest') fig.colorbar(pcm, ax=ax[0], extend='max') pcm = ax[1].pcolor(X, Y, Z, cmap='PuBu_r', shading='nearest') fig.colorbar(pcm, ax=ax[1], extend='max') .. image-sg:: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_001.png :alt: colormap normalizations :srcset: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_001.png, /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_001_2_0x.png 2.0x :class: sphx-glr-single-img .. rst-class:: sphx-glr-script-out .. code-block:: none .. GENERATED FROM PYTHON SOURCE LINES 42-44 PowerNorm: Here a power-law trend in X partially obscures a rectified sine wave in Y. We can remove the power law using a PowerNorm. .. GENERATED FROM PYTHON SOURCE LINES 44-57 .. code-block:: default X, Y = np.mgrid[0:3:complex(0, N), 0:2:complex(0, N)] Z1 = (1 + np.sin(Y * 10.)) * X**2 fig, ax = plt.subplots(2, 1) pcm = ax[0].pcolormesh(X, Y, Z1, norm=colors.PowerNorm(gamma=1. / 2.), cmap='PuBu_r', shading='nearest') fig.colorbar(pcm, ax=ax[0], extend='max') pcm = ax[1].pcolormesh(X, Y, Z1, cmap='PuBu_r', shading='nearest') fig.colorbar(pcm, ax=ax[1], extend='max') .. image-sg:: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_002.png :alt: colormap normalizations :srcset: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_002.png, /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_002_2_0x.png 2.0x :class: sphx-glr-single-img .. rst-class:: sphx-glr-script-out .. code-block:: none .. GENERATED FROM PYTHON SOURCE LINES 58-64 SymLogNorm: two humps, one negative and one positive, The positive with 5-times the amplitude. Linearly, you cannot see detail in the negative hump. Here we logarithmically scale the positive and negative data separately. Note that colorbar labels do not come out looking very good. .. GENERATED FROM PYTHON SOURCE LINES 64-82 .. code-block:: default X, Y = np.mgrid[-3:3:complex(0, N), -2:2:complex(0, N)] Z1 = 5 * np.exp(-X**2 - Y**2) Z2 = np.exp(-(X - 1)**2 - (Y - 1)**2) Z = (Z1 - Z2) * 2 fig, ax = plt.subplots(2, 1) pcm = ax[0].pcolormesh(X, Y, Z1, norm=colors.SymLogNorm(linthresh=0.03, linscale=0.03, vmin=-1.0, vmax=1.0, base=10), cmap='RdBu_r', shading='nearest') fig.colorbar(pcm, ax=ax[0], extend='both') pcm = ax[1].pcolormesh(X, Y, Z1, cmap='RdBu_r', vmin=-np.max(Z1), shading='nearest') fig.colorbar(pcm, ax=ax[1], extend='both') .. image-sg:: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_003.png :alt: colormap normalizations :srcset: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_003.png, /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_003_2_0x.png 2.0x :class: sphx-glr-single-img .. rst-class:: sphx-glr-script-out .. code-block:: none .. GENERATED FROM PYTHON SOURCE LINES 83-86 Custom Norm: An example with a customized normalization. This one uses the example above, and normalizes the negative data differently from the positive. .. GENERATED FROM PYTHON SOURCE LINES 86-120 .. code-block:: default X, Y = np.mgrid[-3:3:complex(0, N), -2:2:complex(0, N)] Z1 = np.exp(-X**2 - Y**2) Z2 = np.exp(-(X - 1)**2 - (Y - 1)**2) Z = (Z1 - Z2) * 2 # Example of making your own norm. Also see matplotlib.colors. # From Joe Kington: This one gives two different linear ramps: class MidpointNormalize(colors.Normalize): def __init__(self, vmin=None, vmax=None, midpoint=None, clip=False): self.midpoint = midpoint super().__init__(vmin, vmax, clip) def __call__(self, value, clip=None): # I'm ignoring masked values and all kinds of edge cases to make a # simple example... x, y = [self.vmin, self.midpoint, self.vmax], [0, 0.5, 1] return np.ma.masked_array(np.interp(value, x, y)) ##### fig, ax = plt.subplots(2, 1) pcm = ax[0].pcolormesh(X, Y, Z, norm=MidpointNormalize(midpoint=0.), cmap='RdBu_r', shading='nearest') fig.colorbar(pcm, ax=ax[0], extend='both') pcm = ax[1].pcolormesh(X, Y, Z, cmap='RdBu_r', vmin=-np.max(Z), shading='nearest') fig.colorbar(pcm, ax=ax[1], extend='both') .. image-sg:: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_004.png :alt: colormap normalizations :srcset: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_004.png, /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_004_2_0x.png 2.0x :class: sphx-glr-single-img .. rst-class:: sphx-glr-script-out .. code-block:: none .. GENERATED FROM PYTHON SOURCE LINES 121-124 BoundaryNorm: For this one you provide the boundaries for your colors, and the Norm puts the first color in between the first pair, the second color between the second pair, etc. .. GENERATED FROM PYTHON SOURCE LINES 124-146 .. code-block:: default fig, ax = plt.subplots(3, 1, figsize=(8, 8)) ax = ax.flatten() # even bounds gives a contour-like effect bounds = np.linspace(-1, 1, 10) norm = colors.BoundaryNorm(boundaries=bounds, ncolors=256) pcm = ax[0].pcolormesh(X, Y, Z, norm=norm, cmap='RdBu_r', shading='nearest') fig.colorbar(pcm, ax=ax[0], extend='both', orientation='vertical') # uneven bounds changes the colormapping: bounds = np.array([-0.25, -0.125, 0, 0.5, 1]) norm = colors.BoundaryNorm(boundaries=bounds, ncolors=256) pcm = ax[1].pcolormesh(X, Y, Z, norm=norm, cmap='RdBu_r', shading='nearest') fig.colorbar(pcm, ax=ax[1], extend='both', orientation='vertical') pcm = ax[2].pcolormesh(X, Y, Z, cmap='RdBu_r', vmin=-np.max(Z1), shading='nearest') fig.colorbar(pcm, ax=ax[2], extend='both', orientation='vertical') plt.show() .. image-sg:: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_005.png :alt: colormap normalizations :srcset: /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_005.png, /gallery/images_contours_and_fields/images/sphx_glr_colormap_normalizations_005_2_0x.png 2.0x :class: sphx-glr-single-img .. rst-class:: sphx-glr-timing **Total running time of the script:** ( 0 minutes 3.715 seconds) .. _sphx_glr_download_gallery_images_contours_and_fields_colormap_normalizations.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: colormap_normalizations.py ` .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: colormap_normalizations.ipynb ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_