.. _pylab_examples-log_demo:

pylab_examples example code: log_demo.py
========================================



.. plot:: /home/tcaswell/source/p/matplotlib/doc/mpl_examples/pylab_examples/log_demo.py

::

    
    import numpy as np
    import matplotlib.pyplot as plt
    
    plt.subplots_adjust(hspace=0.4)
    t = np.arange(0.01, 20.0, 0.01)
    
    # log y axis
    plt.subplot(221)
    plt.semilogy(t, np.exp(-t/5.0))
    plt.title('semilogy')
    plt.grid(True)
    
    # log x axis
    plt.subplot(222)
    plt.semilogx(t, np.sin(2*np.pi*t))
    plt.title('semilogx')
    plt.grid(True)
    
    # log x and y axis
    plt.subplot(223)
    plt.loglog(t, 20*np.exp(-t/10.0), basex=2)
    plt.grid(True)
    plt.title('loglog base 2 on x')
    
    # with errorbars: clip non-positive values
    ax = plt.subplot(224)
    ax.set_xscale("log", nonposx='clip')
    ax.set_yscale("log", nonposy='clip')
    
    x = 10.0**np.linspace(0.0, 2.0, 20)
    y = x**2.0
    plt.errorbar(x, y, xerr=0.1*x, yerr=5.0 + 0.75*y)
    ax.set_ylim(ymin=0.1)
    ax.set_title('Errorbars go negative')
    
    
    plt.show()
    

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