Plotting options in Python

Clawpack 4.4 includes utilities for plotting using Python. Most of these are defined in the file $CLAW/python/pyclaw/plotters/ In order to use these you will need to insure that you have the required modules installed (see Installation of required modules).

Clawpack 4.4 also includes the Matlab plotting tools from 4.3 and before, see Plotting using Matlab.

The advantages of using the Python options are:

  • Python and the graphics modules used in Clawpack are open source. Since Clawpack itself is open source we find it desirable to also have an open source plotting open for viewing the results.

  • The Python tools developed so far (mostly for 1d and 2d data sets) are more powerful than the Matlab versions they replace, and can be used for example to automatically generate html versions of multiple plots each frame over all frames of a computation, to generate latex versions of the output, as well as to step through the frames one by one as with the Matlab tools. It is easier to specify a set of multiple plots to be produced for each frame.

  • Matlab graphics are somewhat limited for 3d data sets, whereas several open source visualization tools such as VisIt (developed at Lawrence Livermore National Laboratory) are much better for dealing with large data sets, AMR grids, etc. VisIt has Python bindings and we are currently extending our tools to work with VisIt. If you are already a VisIt user, note that VisIt has a Claw reader that can be used to import data from Clawpack, see Application Toolkit Formats.

    We are also considering developing tools for use with Mayavi.

  • Python is a powerful language that can be scripted to perform multiple runs, such as in a convergence test, and collect the results in tables or plots. We are developing tools to simplify this process.

See Python Hints for more information on Python and pointers to many tutorials.

Producing html plots from the command line

In most Clawpack directories, typing:

$  make .plots

will compile the code and run it (if necessary) and then produce a set of html files that can be used to view the resulting plots. These will be in a subdirectory of the current directory as specified by CLAW_PLOTDIR in the Makefile.

Viewing plots via a local web server

The best way to view the plots and associated web pages for each example is to first start a python web server in your main $CLAW directory with the commands:

$ cd $CLAW
$ xterm -e python python/ & # to start server in new X window

The main $CLAW directory will then be available at http://localhost:50005 and jsMath should work properly to display latex on the webpages (once you’ve downloaded the required fonts, see

Producing a latex file with plots from the command line

A latex file with all the plots can also be produced by printframes function, and is also typically controlled by options set in the file

Setting plot parameters with a setplot function

Typically each applications directory contains a file, see for example Plotting examples in 1d. This file should define a function setplot(plotdata) that sets various attributes of an object plotdata of class ClawPlotData.

Documentation on how to create a setplot function and the various plotting parameters that can be set can be found in the section Using to specify the desired plots.

Examples can be found at Plotting examples in 1d.

Interactive plotting with Iplotclaw

For interactive plotting we suggest using IPython, which is a nicer shell than the pure python shell, with things like command completion and history. See the IPython Documentation for more information and IPython configuration for information on configuring it to use with Clawpack.

Note that to use interactive plotting must give the –pylab flag in order for plotting to work properly, and that this automatically imports numpy and matplotlib commands into your namespace, so you can use, for example, linspace or pcolor without further imports.

Here’s an example:

$ ipython --pylab

In [1]: from pyclaw.plotters.Iplotclaw import Iplotclaw
In [2]: ip = Iplotclaw()
In [3]: ip.plotloop()
Executing setplot ...

Interactive plotclaw with ndim = 1 ...
Type ? at PLOTCLAW prompt for list of commands

    Start at which frame [default=0] ?
    Plotting frame 0 ...
    Plotting frame 1 ...
In [4]:

Type ? at the PLOTCLAW prompt or ?command-name for more information. Most commonly used are n for next frame, p for previous frame and j to jump to a different frame. Hitting return at the prompt repeats the previous command.

By default Iplotclaw attempts to determine the directory where output can be found by examining the file .output that is automatically created by the make .output command. If not found, the default is to look in the current directory. Instead you can provide an argument outdir to specify the directory for output.

By default Iplotclaw attempts to execute a setplot function from a file Instead you can provide an argument setplot to specify the file name.


In [2]: ip = Iplotclaw(setplot='', outdir='_output2')

You can restart the plotloop later by doing:

In [4]: ip.plotloop()

Interactive plotting for Clawpack output...
Plotting data from outdir =  _output
Type ? at PLOTCLAW prompt for list of commands

    Start at which frame [default=1] ?
    Replot data for frame 1 [no] ?

By default it starts at the frame where you previously left off.

If you want to change plot parameters, the easiest way is to edit the file, either in a different window or, if you use vi, by:


and then re-execute the setplot function using:

PLOTCLAW > resetplot

If you recompute results by running the fortran code again and want to plot the new results (from this same directory), you may have to clear the frames that have already been viewed using:

PLOTCLAW > clearframes

Or you can redraw the frame you’re currently looking at without clearing the rest of the cached frame data by doing:


To see what figures, axes, and items have been defined by setplot:


Current plot figures, axes, and items:
  figname = Pressure, figno = 1
     axesname = AXES1, axescmd = subplot(1,1,1)
        itemname = ITEM1,  plot_type = 1d_plot

  figname = Velocity, figno = 2
     axesname = AXES1, axescmd = subplot(1,1,1)
        itemname = ITEM1,  plot_type = 1d_plot

Type “help” or “help command-name” at the prompt for more options.

Access to current_data

If you are viewing plots in using Iplotclaw and want to explore the data for some frame or make plots directly in your Python shell, the data that is being plotted is available to you in attributes of the Iplotclaw instance. For example:

>>> ip = Iplotclaw();  ip.plotloop()

Interactive plotting for Clawpack output...

Plotting data from outdir =  _output
    Plotting Frame 0 at t = 0.0

>>> pd = ip.plotdata
>>> current_data = ip.current_data

The current_data object contains the current_data used for the most recent plot, while pd is the ClawPlotData object that gives access to all the plotting parameters currently being used as well as to methods such as getframe for retrieving other frames of data from this computation.

If you want to change the directory outdir where the frame data is coming from, you could do, for example:

>>> pd.outdir = "_output2"
>>> ip.plotloop()
PLOTCLAW > clearframes    # to remove old frames from cache
PLOTCLAW > rr             # to redraw current frame number but with new data

IPython configuration

The IPython configuration system changed substantially in IPython Version 0.11 and Clawpack no longer contains the configuration files that used to be found in $CLAW/python/ipythondir.

See the documentation for the version of IPython you are using.

The instructions below are for recent versions. See IPython Configuration Overview and Configuring IPython for more complete details.

It is suggested that you create a directory .ipython in your home directory if you do not already have one, and set the IPYTHONDIR environment variable to point here, e.g. in bash:

$ export IPYTHONDIR=$HOME/.ipython

If you haven’t created a default profile in the past you might want to do so:

$ ipython profile create

Then create an IPython configuration for Clawpack via the command:

$ ipython profile create clawpack

There will now be a directory $HOME/.ipython/profile_clawpack containing a file with the default configuration. Replace this file with the version in $CLAW/python/ This doesn’t do anything fancy, but does execute the command

from pyclaw.plotters.Iplotclaw import Iplotclaw

whenever you start IPython with this configuration, saving you one line of typing. You can of course modify this profile to add anything else you wish, as described in the IPython documentation.

Now you can start IPython via:

$ ipython --pylab --profile=clawpack

to use this profile.

You might want to define an alias in your .bashrc file for the above invocation, e.g.

alias ipyclaw='ipython --pylab --profile=clawpack'

so then you can just do:

$ ipyclaw

to start IPython.


The function pyclaw.plotters.frametools.printframes can be used to produce html and latex versions of the plots:

>>> from import ClawPlotData
>>> from pyclaw.plotters import frametools
>>> plotclaw = ClawPlotData()
>>> # set attributes as desired
>>> frametools.printframes(plotclaw)

A convenience method of ClawPlotData is defined to apply this function, e.g.:

>>> plotclaw.printframes()

This function is automatically called by the “make .plots” option available in most examples.

Specifying what and how to plot

The first step in specifying how to plot is to create a ClawPlotData object to hold all the data required for plotting. This is generally done one of two ways:

  1. In a script such as the script included in most example directories, e.g., claw/examples/acoustics/1d/example1/

  2. By creating an instance of Iplotclaw to do interactive plotting, e.g.:

    >>> ip = Iplotclaw()

    Then ip will have an attribute plotdata that is a ClawPlotData object. This object will have attribute setplot initialized to ‘’, indicating that other attributes should be set by executing the setplot function defined in the file ‘’ in this directory.

Once you have a ClawPlotData object you can set various attributes to control what is plotted. For example,:

>>> plotdata.plotdir = '_plots'
>>> plotdata.setplot = ''

will cause hardcopy to go to subdirectory _plots of the current directory and will cause the plotting routines to execute:

>>> from my_setplot_file import setplot
>>> plotdata = setplot(plotdata)

before doing the plotting.

There are many other ClawPlotData attributes and methods.

Most example directories contain a file that contains a function setplot(). This function sets various attributes of the ClawPlotData object to control what figures, axes, and items should be plotted for each frame of the solution.

For an outline of how a typical set of plots is specified, see Using to specify the desired plots.