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# Demo Curvelinear Grid2

Custom grid and ticklines.

This example demonstrates how to use GridHelperCurveLinear to define custom grids and ticklines by applying a transformation on the grid. As showcase on the plot, a 5x5 matrix is displayed on the axes.

    import numpy as np
    import matplotlib.pyplot as plt

    from mpl_toolkits.axisartist.grid_helper_curvelinear import \
        GridHelperCurveLinear
    from mpl_toolkits.axisartist.axislines import Subplot

    import mpl_toolkits.axisartist.angle_helper as angle_helper

    def curvelinear_test1(fig):
        """
        grid for custom transform.
        """

        def tr(x, y):
            sgn = np.sign(x)
            x, y = np.abs(np.asarray(x)), np.asarray(y)
            return sgn*x**.5, y

        def inv_tr(x, y):
            sgn = np.sign(x)
            x, y = np.asarray(x), np.asarray(y)
            return sgn*x**2, y

        extreme_finder = angle_helper.ExtremeFinderCycle(20, 20,
                                                         lon_cycle=None,
                                                         lat_cycle=None,
                                                         # (0, np.inf),
                                                         lon_minmax=None,
                                                         lat_minmax=None,
                                                         )

        grid_helper = GridHelperCurveLinear((tr, inv_tr),
                                            extreme_finder=extreme_finder)

        ax1 = Subplot(fig, 111, grid_helper=grid_helper)
        # ax1 will have a ticks and gridlines defined by the given
        # transform (+ transData of the Axes). Note that the transform of
        # the Axes itself (i.e., transData) is not affected by the given
        # transform.

        fig.add_subplot(ax1)

        ax1.imshow(np.arange(25).reshape(5, 5),
                   vmax=50, cmap=plt.cm.gray_r,
                   interpolation="nearest",
                   origin="lower")

        # tick density
        grid_helper.grid_finder.grid_locator1._nbins = 6
        grid_helper.grid_finder.grid_locator2._nbins = 6

    if 1:
        fig = plt.figure(1, figsize=(7, 4))
        fig.clf()

        curvelinear_test1(fig)
        plt.show()

Total running time of the script: ( 0 minutes 0.039 seconds)

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