.. _pylab_examples-transoffset:

pylab_examples example code: transoffset.py
===========================================



.. plot:: /home/tcaswell/src/p/matplotlib/doc/mpl_examples/pylab_examples/transoffset.py

::

    '''
    This illustrates the use of transforms.offset_copy to
    make a transform that positions a drawing element such as
    a text string at a specified offset in screen coordinates
    (dots or inches) relative to a location given in any
    coordinates.
    
    Every Artist--the mpl class from which classes such as
    Text and Line are derived--has a transform that can be
    set when the Artist is created, such as by the corresponding
    pyplot command.  By default this is usually the Axes.transData
    transform, going from data units to screen dots.  We can
    use the offset_copy function to make a modified copy of
    this transform, where the modification consists of an
    offset.
    '''
    
    import matplotlib.pyplot as plt
    import matplotlib.transforms as mtrans
    import numpy as np
    
    from matplotlib.transforms import offset_copy
    
    xs = np.arange(7)
    ys = xs**2
    
    fig = plt.figure(figsize=(5, 10))
    ax = plt.subplot(2, 1, 1)
    
    # If we want the same offset for each text instance,
    # we only need to make one transform.  To get the
    # transform argument to offset_copy, we need to make the axes
    # first; the subplot command above is one way to do this.
    trans_offset = mtrans.offset_copy(ax.transData, fig=fig,
                                      x=0.05, y=0.10, units='inches')
    
    for x, y in zip(xs, ys):
        plt.plot((x,), (y,), 'ro')
        plt.text(x, y, '%d, %d' % (int(x), int(y)), transform=trans_offset)
    
    
    # offset_copy works for polar plots also.
    ax = plt.subplot(2, 1, 2, projection='polar')
    
    trans_offset = mtrans.offset_copy(ax.transData, fig=fig, y=6, units='dots')
    
    for x, y in zip(xs, ys):
        plt.polar((x,), (y,), 'ro')
        plt.text(x, y, '%d, %d' % (int(x), int(y)),
                 transform=trans_offset,
                 horizontalalignment='center',
                 verticalalignment='bottom')
    
    plt.show()
    

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