.. _subplots_axes_and_figures-fahrenheit_celsius_scales:

subplots_axes_and_figures example code: fahrenheit_celsius_scales.py
====================================================================



.. plot:: /build/tmp/matplotlib-1.4.2/doc/mpl_examples/subplots_axes_and_figures/fahrenheit_celsius_scales.py

::

    """
    Demo of how to display two scales on the left and right y axis.
    
    This example uses the Fahrenheit and Celsius scales.
    """
    import matplotlib.pyplot as plt
    import numpy as np
    
    
    def fahrenheit2celsius(temp):
        """
        Returns temperature in Celsius.
        """
        return (5. / 9.) * (temp - 32)
    
    
    def convert_ax_c_to_celsius(ax_f):
        """
        Update second axis according with first axis.
        """
        y1, y2 = ax_f.get_ylim()
        ax_c.set_ylim(fahrenheit2celsius(y1), fahrenheit2celsius(y2))
        ax_c.figure.canvas.draw()
    
    fig, ax_f = plt.subplots()
    ax_c = ax_f.twinx()
    
    # automatically update ylim of ax2 when ylim of ax1 changes.
    ax_f.callbacks.connect("ylim_changed", convert_ax_c_to_celsius)
    ax_f.plot(np.linspace(-40, 120, 100))
    ax_f.set_xlim(0, 100)
    
    ax_f.set_title('Two scales: Fahrenheit and Celsius')
    ax_f.set_ylabel('Fahrenheit')
    ax_c.set_ylabel('Celsius')
    
    plt.show()
    

Keywords: python, matplotlib, pylab, example, codex (see :ref:`how-to-search-examples`)