.. _statistics-errorbar_demo_features:

statistics example code: errorbar_demo_features.py
==================================================



.. plot:: /builddir/build/BUILD/matplotlib-1.3.1/doc/mpl_examples/statistics/errorbar_demo_features.py

::

    """
    Demo of errorbar function with different ways of specifying error bars.
    
    Errors can be specified as a constant value (as shown in `errorbar_demo.py`),
    or as demonstrated in this example, they can be specified by an N x 1 or 2 x N,
    where N is the number of data points.
    
    N x 1:
        Error varies for each point, but the error values are symmetric (i.e. the
        lower and upper values are equal).
    
    2 x N:
        Error varies for each point, and the lower and upper limits (in that order)
        are different (asymmetric case)
    
    In addition, this example demonstrates how to use log scale with errorbar.
    """
    import numpy as np
    import matplotlib.pyplot as plt
    
    # example data
    x = np.arange(0.1, 4, 0.5)
    y = np.exp(-x)
    # example error bar values that vary with x-position
    error = 0.1 + 0.2 * x
    # error bar values w/ different -/+ errors
    lower_error = 0.4 * error
    upper_error = error
    asymmetric_error = [lower_error, upper_error]
    
    fig, (ax0, ax1) = plt.subplots(nrows=2, sharex=True)
    ax0.errorbar(x, y, yerr=error, fmt='-o')
    ax0.set_title('variable, symmetric error')
    
    ax1.errorbar(x, y, xerr=asymmetric_error, fmt='o')
    ax1.set_title('variable, asymmetric error')
    ax1.set_yscale('log')
    plt.show()
    
    

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