News for Octave Version 3

Compatibility with Matlab graphics is much better. We now have some graphics features that work like Matlab's Handle Graphics (tm):
- You can make a subplot and then use the print function to generate file with the plot.
- RGB line colors are supported if you use gnuplot 4.2. Octave can still use gnuplot 4.0, but there is no way to set arbitrary line colors with it when using the Matlab-style plot functions. There never was any way to do this reliably with older versions of gnuplot (whether run from Octave or not) since it only provided a limited set to choose from, and they were terminal dependent, so choosing color 1 with the X11 terminal would be different from color 1 with the PostScript terminal. Valid RGB colors for gnuplot 4.0 are the eight possible combinations of 0 and 1 for the R, G and B values. Invalid values are all mapped to the same color.
  This also affects patch objects used in the bar, countour, meshc and surfc functions, where the bars and contours will be monochrome. A workaround for this is to type "colormap gmap40" that loads a colormap that in many cases will be adequate for simple bar and contour plots.
- You can control the width of lines using (for example):
```
	line (x, y, "linewidth", 4, "color", [1, 0, 0.5]);
```
  (this also shows the color feature).
- With gnuplot 4.2, image data is plotted with gnuplot and may be combined with other 2-d plot data.
- Lines for contour plots are generated with an Octave function, so contour plots are now 2-d plots instead of special 3-d plots, and this allows you to plot additional 2-d data on top of a contour plot.
- With the gnuplot "extended" terminals the TeX interpreter is emulated. However, this means that the TeX interpreter is only supported on the postscript terminals with gnuplot 4.0. Under gnuplot 4.2 the terminals aqua, dumb, png, jpeg, gif, pm, windows, wxt, svg and x11 are supported as well.
- The following plot commands are now considered obsolete and will be removed from a future version of Octave:
```
	__gnuplot_set__
	__gnuplot_show__
	__gnuplot_plot__
	__gnuplot_splot__
	__gnuplot_replot__
```
  Additionally, these functions no longer have any effect on plots created with the Matlab-style plot commands (plot, line, mesh, semilogx, etc.).
- Plot property values are not extensively checked. Specifying invalid property values may produce unpredictible results.
- Octave now sends data over the same pipe that is used to send commands to gnuplot. While this avoids the problem of cluttering /tmp with data files, it is no longer possible to use the mouse to zoom in on plots. This is a limitation of gnuplot, which is unable to zoom when the data it plots is not stored in a file. Some work has been done to fix this problem in newer versions of gnuplot (> 4.2.2). See for example, this thread on the gnuplot development list.
The way Octave handles search paths has changed. Instead of setting the built-in variable LOADPATH, you must use addpath, rmpath, or path to manipulate the function search path. These functions will maintain "." at the head of the path, for compatibility with Matlab.
Leading, trailing or doubled colons are no longer special. Now, all elements of the search path are explicitly included in the path when Octave starts. To display the path, use the path function.
Path elements that end in // are no longer searched recursively. Instead, you may use addpath and the genpath function to add an entire directory tree to the path. For example,
```
      addpath (genpath ("~/octave"));
```
will add ~/octave and all directories below it to the head of the path.
Previous versions of Octave had a number of built-in variables to control warnings (for example, warn_divide_by_zero). These variables have been replaced by warning identifiers that are used with the warning function to control the state of warnings.
For example, instead of writing
```
      warn_divide_by_zero = false;
```
to disable divide-by-zero warnings, you should write
```
      warning ("off", "Octave:divide-by-zero");
```
You may use the same technique in your own code to control warnings. For example, you can use
```
      warning ("My-package:phase-of-the-moon",
               "the phase of the moon could cause trouble today");
```
to allow users to control this warning using the "My-package:phase-of-the-moon" warning identifier.
You may also enable or disable all warnings, or turn them into errors:
```
      warning ("on", "all");
      warning ("off", "all");
      warning ("error", "Octave:divide-by-zero");
      warning ("error", "all");
```
You can query the state of current warnings using
```
      warning ("query", ID)
      warning ("query")
```
(only those warning IDs which have been explicitly set are returned).
A partial list and description of warning identifiers is available using
```
      help warning_ids
```
All built-in variables have been converted to functions. This change simplifies the interpreter and allows a consistent interface to internal variables for user-defined packages and the core functions distributed with Octave. In most cases, code that simply accesses internal variables does not need to change. Code that sets internal variables will change. For example, instead of writing
```
      PS1 = ">> ";
```
you will need to write
```
      PS1 (">> ");
```
If you need write code that will run in both old and new versions of Octave, you can use something like
```
      if (exist ("OCTAVE_VERSION") == 5)
        ## New:
        PS1 (">> ");
      else
        ## Old:
        PS1 = ">> ";
      endif
```
For compatibility with Matlab, the output order of Octave's "system" function has changed from
```
      [output, status] = system (cmd);
```
to
```
      [status, output] = system (cmd);
```
For compatibility with Matlab, normcdf, norminv, normpdf, and normrnd have been modified to compute distributions using the standard deviation instead of the variance.
For compatibility with Matlab, the output of Octave's fsolve function has been changed from
```
      [x, info, msg] = fsolve (...);
```
to
```
      [x, fval, info] = fsolve (...);
```
For compatibility with Matlab, normcdf, norminv, normpdf, and normrnd have been modified to compute distributions using the standard deviation instead of the variance.
For compatibility with Matlab, gamcdf, gaminv, gampdf, gamrnd, expcdf, expinv, exppdf and exprnd have been modified to compute the distributions using the standard scale factor rather than one over the scale factor.