Default colors




The first thing most users notice when running plt for the first time is that the traces are plotted on a black background. In fact this can be shocking at first because it is so different from the traditional Windows and Matlab standard color scheme that you may have grown used to. Rest assured however that you are not forced into any color scheme. The next section explains why you may not want to change the defaults, and the section after that explains how this is easily done if you prefer to ignore that advice.

The advantage of the default plt color scheme

The primary virtue of plt's default black plotting background is that you can distinguish far more traces based on color alone when compared with Matlab's default white plotting background.

Why is this? Consider the green trace for example. The plt default uses [0 1 0] for the green trace as you would expect. However with the standard Matlab color scheme, the green trace is not [0 1 0] because that is too bright and yields low contrast against the white background. So instead they use [0 .5 0]. But this means that the green is less saturated making it more difficult to distinguish the green from say a black or dark grey. Similar problems happen with some other colors. This is why the Matlab default trace color order only includes seven different colors. Once you define an 8th trace it cycles back around and uses the same color as the first trace. Especially with the thin traces commonly used, seven is about the maximum number of colors most people can distinguish and even that is not easy. However with a black background and when using plt's carefully chosen default trace colors it is not difficult to distinguish at least three times as many traces based on color alone.

To see that this is true, open the pltn example with 20 traces enabled (i.e. type pltn(20) at the command prompt). Now see if you can match up all 20 traces with the respective trace labels in the TraceID box. If you aren't seriously color blind you probably will find this task easy. Now use the edit box below the TraceID box to change the number of lines to 40. (The 40 trace colors that will be used are shown to the left.) If you have sharp color vision you still probably can identify all 40 traces just by the trace color. You will find that if you switch to a white plotting background, you will be able to identify far fewer traces based on the trace color no matter what trace color sequence you choose. Matlab's standard plot routine doesn't have features that encourage the use of so many traces, and so you probably haven't noticed this problem with the white plot background. However, plt was designed to work well with many dozens of traces and you will likely take advantage of this capability soon ... and in the process you will come to appreciate plt's default color scheme.

Configuring plt to use Matlab default colors (color specification files)

When you type a command into the command window such as plt(x,y) the data specified will be plotted using plt's default colors (i.e. dark background). However if even after reading the previous section you would rather it plot the data using Matlab's default colors, the easiest way to do this is to rename the file pltColor1.mat in the plt folder to pltColor.mat. This is a "color specification file" whose contents are described in the section below. Every time you enter a plt command from the command window, plt will look for this file (pltColor.mat in the plt folder) and will use the specified colors if the file exists. This particular file (until you change it with the methods described below) specifies colors that are the same as Matlab's default color selections.

If you call plt from a Matlab script or function file then plt will not use the pltColor.mat file; however, it will look for a different color specification file. Suppose you write a Matlab script called FooPlot.m that contains a call to plt. Then plt will look for a color specification file called FooPlotColor.mat. This file must be located in the same folder that contains FooPlot.m. So to make FooPlot use the default colors, you could copy pltColor1.mat to FooPlot.m. This can also be accomplished by including the 'ColorDef',0 parameter in the plt argument list, however the color specification file method is better if you want to allow the user to easily modify the program's colors from the its graphical interface.

There is one other special color specification file that you can use named pltColorAll.mat. If this file exists in the plt folder it will be used by plt no matter which script or function it is called from and even when plt is entered from the command line. However the colors specified by pltColorAll.mat may be overridden by several methods:

Creating or modifying a color specification file

Start by opening any plt figure. It will be easier if you choose a plt figure that is already using colors that is close to what you want. To edit one of the trace colors: Once the color file is created, you may rename it to pltColorAll.mat if you want it to apply to all your script and function files. Although it is usually easier to edit the colors by the method described above, you can also manually edit the colors in the Matlab command window. For example, if you type:

clear; cd plt; load pltColor; who;

you will see the following list of variables from the file:

cTRACE - Trace colors (an N x 3 matrix, where N is the number of traces in the TraceID box)
cFIGbk - Figure background color
cPLTbk - Plot background color
cXYax  - Axis border color
cXYlbl - Axis label color
cDELTA - Delta cursor color

After editing the variables you want to modify, type save pltColor to make the changes permanent.

The menus used to edit these colors are also described in the Menu box and menu bar section. There you will also find that there are other ways of accessing those menus which perhaps you will find more convenient.