• 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.

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.

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 

      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 

      [output, status] = system (cmd); 

to

      [status, output] = system (cmd); 

      [x, info, msg] = fsolve (...); 

to

      [x, fval, info] = fsolve (...);