The QtiPlot Handbook
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# Contour Curves Options

This dialog is activated by clicking on a contour curve (or on the plotting area) when a 3D plot has been created from a matrix with one of the following commands from the Plot 3D menu: Contour+Color Fill command, Countour Lines command or Gray Scale Map command.

Figure 5-16. The Values tab.

The Values tab allows choosing the matrix that is to serve as the data source for the plot. It is possible to use a formula defined for the matrix to calculate the plotted Z values by checking the Use matrix formula to calculate values box. This results in higher accuracy, especially when drawing contour lines, but it only works if the formula uses muParser compatible syntax.

Figure 5-17. The Colors Tab.

There are two groups of controls on this tab. Each group is activated by checking the box next to the group label. The first group of controls, labeled Image, are used to select the fill type of the contour plot. It is checked when filling of the contour plot is desired. If unchecked, no fill will be used. If filling is enabled, you may choose between gray-scale, a default color mapping and a custom color mapping with the 3 radio buttons. The default gray-scale and color maps are shown in the figure below.

You can only customize the colormap when the Custom Colors option is selected. A table with a set of numbers (the Z levels), and the color corresponding to each Z level, is presented. You can then add, remove or modify levels from the definition of the colormap. The first and last levels cannot be changed. These are always set to the minimum and maximum Z values. Note that this is only the definition of the colormap - it won't change the number of contour lines in your plot. An example of classical custom colormap is given here:

As long as the Scale Colors checkbox remains checked, Z-values that fall between colormap levels will be displayed in colors that are interpolated between the colors defined for the bounding levels. It is also possible to define discrete colors for each level. To do this you must uncheck the Scale Colors checkbox. In this case, no interpolation will be done, and you must define enough levels in your colormap to produce a desirable result.

The second group of settings must be enabled if you want a bar scale on your plot. You can then define its position and width.

Figure 5-18. The Contour Lines tab.

The Contour Lines tab is used to customize settings applicable to the contour lines. You can select the number of lines and their color. If you check Use Default Pen, the color of the lines will be defined by the settings in the group of controls to the left of the checkbox. If you check Use Color Map, the lines will be colored as a function of the Z levels from the colormap defined in the Colors setting tab. If you check Use Table Custom Pen, the color of the lines will be determined by the settings defined in the Pen column of the table displaying the Z levels.

Figure 5-19. The Labels tab.

The Labels tab is used to enable/disable the display of a Z value for each of the contour lines. You can globally customize the color, background, font, rotation and position of the text labels.

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