.. _plotting:
*********
Plotting
*********
.. currentmodule:: skrf.network
.. contents::
.. ipython::
:suppress:
In [144]: from pylab import *
In [145]: ion()
In [146]: rcParams['savefig.dpi'] = 120
In [147]: rcParams['figure.figsize'] = [4,3]
In [147]: rcParams['figure.subplot.left'] = 0.15
In [147]: clf()
Plotting Methods
-----------------------
Network plotting abilities are implemented as methods of the :class:`Network` class. Some of the plotting functions of network s-parameters are,
.. hlist::
:columns: 2
* :func:`Network.plot_s_re`
* :func:`Network.plot_s_im`
* :func:`Network.plot_s_mag`
* :func:`Network.plot_s_db`
* :func:`Network.plot_s_deg`
* :func:`Network.plot_s_deg_unwrap`
* :func:`Network.plot_s_rad`
* :func:`Network.plot_s_rad_unwrap`
* :func:`Network.plot_s_smith`
* :func:`Network.plot_s_complex`
Similar methods exist for Impedance (:attr:`Network.z`) and Admittance Parameters (:attr:`Network.y`),
.. hlist::
:columns: 2
* :func:`Network.plot_z_re`
* :func:`Network.plot_z_im`
* ...
* :func:`Network.plot_y_re`
* :func:`Network.plot_z_im`
* ...
Step-by-step examples of how to create and customize plots are given
below.
Complex Plots
-----------------------
Smith Chart
+++++++++++++++++
As a first example, load a :class:`~skrf.network.Network` from the
``data`` module, and plot all four s-parameters on the Smith chart.
.. ipython::
In [138]: import skrf as rf
In [139]: from skrf.data import ring_slot
In [139]: ring_slot
@savefig plotting-ring_slot,smith.png
In [139]: ring_slot.plot_s_smith()
.. note::
If you dont see any plots after issuing these commands, then you may not have started ipython with the ``--pylab`` flag. Try ``from pylab import *`` to import the matplotlib commands and ``ion()`` to turn on interactive plotting. See `this page <http://matplotlib.org/users/shell.html>`_ , for more info on ipython's `pylab` mode.
.. note::
Why do my plots look different? See `Formating Plots`_
The smith chart can be drawn with some impedance values labeled through the ``draw_labels`` argument.
.. ipython::
In [139]: figure();
@savefig plotting-ring_slot,smith1.png
In [139]: ring_slot.plot_s_smith(draw_labels=True)
Another common option is to draw addmitance contours, instead of impedance. This is controled through the ``chart_type`` argument.
.. ipython::
In [139]: figure();
@savefig plotting-ring_slot,smith2.png
In [139]: ring_slot.plot_s_smith(chart_type='y')
See :func:`~skrf.plotting.smith` for more info on customizing the Smith Chart.
.. note::
If more than one ``plot_s_smith()`` command is issued on a single figure, you may need to call :func:`draw()` to refresh the chart.
Complex Plane
+++++++++++++++
Network parameters can also be plotted in the complex plane without a Smith Chart through :func:`Network.plot_s_complex`.
.. ipython::
In [138]: figure();
@savefig plotting-ring_slot,complex.png
In [138]: ring_slot.plot_s_complex();
Rectangular Plots
---------------------
Log-Magnitude
++++++++++++++++
Scalar components of the complex network parameters can be plotted vs
frequency as well. To plot the log-magnitude of the s-parameters vs. frequency,
.. ipython::
In [138]: figure();
@savefig plotting-ring_slot,db.png
In [138]: ring_slot.plot_s_db()
When no arguments are passed to the plotting methods, all parameters are plotted. Single parameters can be plotted by passing indecies ``m`` and ``n`` to the plotting commands (indexing start from 0). Comparing the simulated reflection coefficient off the ring slot to a measurement,
.. ipython::
In [138]: from skrf.data import ring_slot_meas
In [138]: figure();
In [138]: ring_slot.plot_s_db(m=0,n=0) # s11
@savefig plotting-ring_slot,db2.png
In [138]: ring_slot_meas.plot_s_db(m=0,n=0) # s11
See `Customizing Plots`_ for more information on customization.
Phase
++++++++++++++++
Plot phase,
.. ipython::
In [138]: figure();
@savefig plotting-ring_slot,deg.png
In [138]: ring_slot.plot_s_deg()
Or unwrapped phase,
.. ipython::
In [138]: figure();
@savefig plotting-ring_slot,deg_unwrap.png
In [138]: ring_slot.plot_s_deg_unwrap()
Impedance, Admittance
++++++++++++++++++++++
The components the Impendanc and Admittance parameters can be plotted
similarly,
.. ipython::
In [138]: figure();
@savefig plotting-ring_slot,z_im.png
In [138]: ring_slot.plot_z_im()
.. ipython::
In [138]: figure();
@savefig plotting-ring_slot,y_re.png
In [138]: ring_slot.plot_y_re()
Customizing Plots
-------------------
The legend entries are automatically filled in with the Network's :attr:`~skrf.network.Network.name`. The entry can be overidden by passing the ``label`` argument to the plot method.
.. ipython::
In [138]: figure();
In [138]: ring_slot.plot_s_db(m=0,n=0, label = 'Simulation')
@savefig plotting-ring_slot,db3.png
In [138]: ring_slot_meas.plot_s_db(m=0,n=0, label = 'Measured')
The frequency unit used on the x-axis is automatically filled in from
the Networks :attr:`~skrf.network.Network.frequency` attribute. To change
the label, change the frequency's ``unit``.
.. ipython::
@verbatim
In [138]: ring_slot.frequency.unit = 'mhz'
Other key word arguments given to the plotting methods are passed through to the matplotlib :func:`~matplotlib.pyplot.plot` function.
.. ipython::
In [138]: figure();
In [138]: ring_slot.plot_s_db(m=0,n=0, linewidth = 3, linestyle = '--', label = 'Simulation')
@savefig plotting-ring_slot,db4.png
In [138]: ring_slot_meas.plot_s_db(m=0,n=0, marker = 'x', markevery = 10,label = 'Measured')
All components of the plots can be customized through `matplotlib <http://matplotlib.sourceforge.net>`_ functions.
.. ipython::
In [138]: figure();
In [138]: ring_slot.plot_s_smith()
In [138]: xlabel('Real Part');
In [138]: ylabel('Imaginary Part');
In [138]: title('Smith Chart');
@savefig plotting-ring_slot,smith3.png
In [139]: draw();
Saving Plots
-------------
Plots can be saved in various file formats using the GUI provided by the matplotlib. However, skrf provides a convenience function, called :func:`~skrf.plotting.save_all_figs`, that allows all open figures to be saved to disk in multiple file formats, with filenames pulled from each figure's title::
>>> rf.save_all_figs('.', format=['eps','pdf'])
./WR-10 Ringslot Array Simulated vs Measured.eps
./WR-10 Ringslot Array Simulated vs Measured.pdf
Misc
---------------
Adding Markers to Lines
++++++++++++++++++++++++++
A common need is to make a color plot, interpretable in greyscale print.
There is a convenient function, :func:`~skrf.plotting.add_markers_to_lines`, which adds markers each line in a plots *after* the plot has been made. In this way, adding markers to an already written set of plotting commands is easy.
.. ipython::
In [138]: figure();
In [138]: ring_slot.plot_s_db(m=0,n=0)
In [138]: ring_slot_meas.plot_s_db(m=0,n=0)
@savefig plotting-ring_slot,db6.png
In [138]: rf.add_markers_to_lines()
Formating Plots
+++++++++++++++++++
It is likely that your plots dont look exactly like the ones in this
tutorial. This is because matplotlib supports a vast amount of `customization <http://matplotlib.org/users/customizing.html>`_. Formating options can be customized `on-the-fly` by modifying values of the ``rcParams`` dictionary. Once these are set to your liking they can be saved to your ``.matplotlibrc`` file.
Here are some relevant parameters which should get your plots looking close to the ones in this tutorial::
my_params = {
'figure.dpi': 120,
'figure.figsize': [4,3],
'figure.subplot.left' : 0.15,
'figure.subplot.right' : 0.9,
'figure.subplot.bottom' : 0.12,
'axes.titlesize' : 'medium',
'axes.labelsize' : 10 ,
'ytick.labelsize' :'small',
'xtick.labelsize' :'small',
'legend.fontsize' : 8 #small,
'legend.loc' : 'best',
'font.size' : 10.0,
'font.family' : 'serif',
'text.usetex' : True, # if you have latex
}
rcParams.update(my_params)
The project `mpltools <http://tonysyu.github.com/mpltools/>`_ provides a way to switch between pre-defined `styles`, and contains other useful plotting-related features.