Ptplot 5.2 is available for demonstration and download from
the Ptplot home page at
http://ptolemy.eecs.berkeley.edu/java/ptplot
Ptplot is a set of two dimensional signal plotter components written
in Java with the following properties:
* Embeddable in applets or applications.
* Auto-ranging.
* Automatic or manual labeling of axes.
* Automatic or manual tick marks.
* Logarithmic axes.
* Live, animated plots.
* Infinite zooming.
* Various plot styles: connected lines, scatter plot, bars, etc.
* Various point styles: none, dots, points, and unique marks.
* Multiple data sets and a legend.
* Color or black and white plotting.
* Error bars.
* Editable plots.
* PlotML, and XML language for specifying plots.
* Compatibility with pxgraph, an older plotting program.
There is a set of demonstrations of the various capabilities. There are
several ways to use the classes in the plot package.
* You can invoke an executable, ptplot, which is a shell script, to plot
data on the local file system or on the network.
* You can invoke an executable, pxgraph, which is a shell script, to
plot data that is stored in binary format compatible with the older
program pxgraph.
* You can invoke a Java application, such as PlotMLApplication, by
setting your CLASSPATH variable appropriately and using the java
executable that is included in your Java distribution.
* You can reference an existing applet class, such as PlotMLApplet, in
an HTML file. The applet parameters, such as dataurl, give the plot
data and format information, either by referring to another file on
the network, or by directly including the information. You do not even
have to have Ptplot installed on your server, since you can always
reference the Berkeley installation.
* You can create new classes derived from applet, frame, or application
classes to customize your plots. This allows you to completely control
the placement of plots on the screen, and to write Java code that
defines the data to be plotted.
The plot data can be specified in any of three data formats:
* PlotML is an XML extension for plot data. Its syntax is similar to
that of HTML.
* An older, simpler syntax for plot data is also provided, although in
the long term, that syntax is unlikely to be maintained (it will not
necessarily be expanded to include new features). For simple data
plots, however, it is adequate. Using it for applets has the advantage
of making it possible to reference a slightly smaller jar file
containing the code, which makes for more responsive applets.
* A binary file format used by the popular pxgraph program, an extension
of xgraph, is supported by classes in the compat package. There is
also a shell script, called pxgraph, which invokes these classes.
Formatting information in pxgraph (and in the compat package) is
provided by command-line arguments, rather than being included with
the plot data, exactly as in the older program. Applets specify these
command-line arguments as an appet parameter.
The main class implementing the plotter component is Plot. It is derived
from PlotBox, which provides only the axes and decorations of the plot.
This is implemented in a base class so that it can be reused for different
kinds of plots. Live (animated) data plots are supported by the PlotLive
class. This class is abstract; a derived class must be created to generate
the data to plot (or collect it from some other application). Editable
plots (where a user can interactively modify the data being plotted) are
supported by the EditablePlot class.
The above classes define panels that are used by placing them into a user
interface context such as an applet or the top-level window of an
application. A number of classes are provided to support common situations,
but you should keep in mind that these classes are by no means
comprehensive. Many interesting uses of the plot package involve writing
Java code to create customized user interfaces that include one or more
plots. The most commonly used built-in classes are those in the plotml
package, which can read PlotML files and the older textual syntax. These
classes are include:
* PlotMLApplet: A simple applet that can read PlotML files off the web
and render them.
* EditablePlotMLApplet: A version that allows editing of any data set in
the plot.
* PlotMLFrame: A top-level window containing a plot defined by a PlotML
file.
* PlotMLApplication: An application that can be invoked from the command
line and reads PlotML files.
* EditablePlotMLApplication: An extension that allows editing of any
data set in the plot.
The last of these is the class invoked by the ptplot command-line script.
It can open plot files, edit them, print them, and save them. There are
simpler version of some of these in the plot package that cannot read
PlotML files, but can read an older, simpler syntax. The only reason to use
these simpler versions is for the slightly smaller jar file sizes, which
can improve the responsivity of applets.
TwoPlotExample is a very simple sample Ptplot application that uses only
core classes in the plot package, and exercises complete control over the
layout of the page.
Backward compatibility with the C pxgraph program is provided in the compat
package by the PxgraphApplet and PxgraphApplication classes in the compat
package.
This code owes a heavy debt to David Harrison, the original author of
xgraph, which runs under the X window system on Unix platforms. An
extension to xgraph called pxgraph, written by Joe Buck, reads binary files
as well as ASCII. For compatibility with these programs, we have provided a
Bourne Shell script called pxgraph that is a drop-in replacement for either
xgraph or pxgraph. Unlike the original program, however, the Java
implementation does not depend on the X window system. We have provided a
DOS batch file called pxgraph.bat that brings pxgraph capability to Windows
platforms.
The changes between Ptplot 5.1 and 5.2 are mainly bug fixes, though
the printing system has been enhanced, and there are a few new method
calls. The list of changes can be found at
http://ptolemy.eecs.berkeley.edu/java/ptplot5.2/ptolemy/plot/doc/changes.htm
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