Python:Plotting

This page will primarily go over some examples of different ways to plot data sets. It assumes

import matplotlib.pyplot as plt

is in the program.

Introduction

The plt.plot() Function

The plt.plot() function is used to plot sets of data on a 2-D grid. What follows comes from matplotlib.pyplot's help function (some paragraphs have been snipped out). The line styles, symbols, and colors are formatted as a clearer table.

plot(*args, **kwargs)
    Plot lines and/or markers to the
    :class:`~matplotlib.axes.Axes`.  *args* is a variable length
    argument, allowing for multiple *x*, *y* pairs with an
    optional format string.  For example, each of the following is
    legal::
    
        plot(x, y)        # plot x and y using default line style and color
        plot(x, y, 'bo')  # plot x and y using blue circle markers
        plot(y)           # plot y using x as index array 0..N-1
        plot(y, 'r+')     # ditto, but with red plusses
    
    If *x* and/or *y* is 2-dimensional, then the corresponding columns
    will be plotted.
    
    If used with labeled data, make sure that the color spec is not
    included as an element in data, as otherwise the last case
    ``plot("v","r", data={"v":..., "r":...)``
    can be interpreted as the first case which would do ``plot(v, r)``
    using the default line style and color.
    
    If not used with labeled data (i.e., without a data argument),
    an arbitrary number of *x*, *y*, *fmt* groups can be specified, as in::
    
        a.plot(x1, y1, 'g^', x2, y2, 'g-')
    
    Return value is a list of lines that were added.
    
    By default, each line is assigned a different style specified by a
    'style cycle'.  To change this behavior, you can edit the
    axes.prop_cycle rcParam.
    
    The following format string characters are accepted to control
    the line style or marker (and) the following color abbreviations are supported:

Line code Meaning - solid : dotted -. dash-dot -- dashed

Symbol code Meaning Symbol code Meaning . point s square , pixel p pentagon o circle * star v triangle (down) h hexagon 1 ^ triangle (up) H hexagon 2 < triangle (left) + plus > triangle (right) x x-mark 1 tri (down) D diamond 2 tri (up) d thin diamond 3 tri (left) vline 4 tri (right) _ hline

Color code Meaning b blue g green r red c cyan m magenta y yellow k black w white

    
    In addition, you can specify colors in many weird and
    wonderful ways, including full names (``'green'``), hex
    strings (``'#008000'``), RGB or RGBA tuples (``(0,1,0,1)``) or
    grayscale intensities as a string (``'0.8'``).  Of these, the
    string specifications can be used in place of a ``fmt`` group,
    but the tuple forms can be used only as ``kwargs``.
    
    Line styles and colors are combined in a single format string, as in
    ``'bo'`` for blue circles.
    
    The *kwargs* can be used to set line properties (any property that has
    a ``set_*`` method).  You can use this to set a line label (for auto
    legends), linewidth, anitialising, marker face color, etc.  Here is an
    example::
    
        plot([1,2,3], [1,2,3], 'go-', label='line 1', linewidth=2)
        plot([1,2,3], [1,4,9], 'rs',  label='line 2')
        axis([0, 4, 0, 10])
        legend()
    
    If you make multiple lines with one plot command, the kwargs
    apply to all those lines, e.g.::
    
        plot(x1, y1, x2, y2, antialiased=False)
    
    Neither line will be antialiased.
    
    You do not need to use format strings, which are just
    abbreviations.  All of the line properties can be controlled
    by keyword arguments.  For example, you can set the color,
    marker, linestyle, and markercolor with::
    
        plot(x, y, color='green', linestyle='dashed', marker='o',
             markerfacecolor='blue', markersize=12).

The plt.savefig() Function

The plt.savefig() function is used to save a plot to a file. The type of sile is determined by the extension of the file name. For example,

plt.savefig('blah.eps')

will save the file to a color Encapsulated PostScript file, while

plt.savefig('blah.pdf')

will save it to a PDF. From the help file for the command, Most backends support png, pdf, ps, eps and svg.

Questions

Post your questions by editing the discussion page of this article. Edit the page, then scroll to the bottom and add a question by putting in the characters *{{Q}}, followed by your question and finally your signature (with four tildes, i.e. ~~~~). Using the {{Q}} will automatically put the page in the category of pages with questions - other editors hoping to help out can then go to that category page to see where the questions are. See the page for Template:Q for details and examples.