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Confidence Region Plot – Options

Use this to set attributes to control the appearance of a Confidence Region Plot.

Graph title

Lets you enter a title for the graph. The title appears centred at the top of the graph. If there are multiple Type of ellipse to plot selected and multiple Probability levels, then the same title will be used for each plot. If you want separate plot titles in this situation, just select one Type of ellipse to plot at a time and change the title for each type.

Title position

Position the title by selecting the Centre, Left or Right option.

Title font

This opens the Edit Font menu that lets you control the font for the title.

Enclose graph in box

Select this to draw an enclosing box around the graph.

Type of ellipse to plot

Assuming a bivariate normal distribution with a Probability level p, the following is expected for the different ellipse types.

Confidence for mean The true bivariate mean will be contained by (100×p)% of the ellipses.
Prediction of future value A future bivariate observation will be contained by (100×p)% of the ellipses.
Equal frequency for observed data (100×p)% of the observed data will be enclosed within the ellipse.

If multiple check boxes are selected, the graph will contain the different types of ellipse, if only one Probability level is given, otherwise separate graphs for each type of ellipse will be produced. At least one ellipse type must be selected.


This selects additional items to display on the plot.

Key A key to the Groups or multiple Y or X variates is added to the plot. The settings for the key can be changed on the Key tab.
Individual data points Plots the individual data points that the ellipses were calculated from. The colours and symbols used for the points are set on the Symbols tab.
Principal axes This adds axes which give the direction of maximum and minimum variation. These will not be at right angles unless the Equal scaling option is selected in the axes tabs

Probability level(s)

This gives the probability that the confidence region covers the true mean or a future point, or one of the data points. This can be a number, a scalar, a list of numbers that are space or comma separated, or a variate. The values must be between 0 and 1. If multiple probabilities are provided, multiple ellipses will be plotted for each level on a single plot.

Number of points in ellipse

This controls the precision of the drawing of the ellipse. Reducing the number of points will speed up the plot, but reduces the accuracy of the drawn ellipse. The default of 1000 gives high enough quality for most purposes. This must be a number between 10 and 10000.

Fill ellipses with colour

If this option is selected, the ellipses are filled with a colour using the transparency value selected. The value must be between 0 and 255. A value of 0 fills the ellipse with a solid/opaque colour so that the points won’t show through. A value of 255 is fully transparent, and is the same as not selecting this option. Values between 150 and 230 will give the best compromise, allowing multiple Probability levels (the higher probabilities will show as denser areas of colour) and the individual points to be seen. When there are Groups or multiple X or Y variates in a plot, the colours used for the fill are controlled by the Colour match for pens option.

Colour match for pens

This option controls the colour of the ellipses when there are Groups or multiple X or Y variates in a plot. If the By groups option is selected, the colours selected in Symbols tab will be used for the ellipses. If the By ellipse type is selected, then the colours given in the Lines colours and styles section will be used for the ellipses.

Line colours and styles

These control the colour and line style used for drawing the ellipses for each of the Type of ellipse to plot options and for the lines for the Principal axes. To change a colour for an item, click its colour button to select a colour from the colour palette dialog. Use the drop-down line style lists to select a line style. Note: the line styles for the ellipses will not be used if the Fill ellipses with colour option is selected.

Edit all fonts as a list

Clicking this opens the Edit All Fonts as a List menu which allows all the fonts in the graph to be set in one place.

Action buttons

Run Produce the graph.
Cancel Close the menu without further changes.
Defaults Reset the options to their default settings.

Action Icons

Pin Controls whether to keep the dialog open when you click Run. When the pin is down  the dialog will remain open, otherwise when the pin is up  the dialog will close.
Restore Restore names into edit fields and default settings.
Clear Clear all fields and list boxes.
Help Open the Help topic for this dialog.

See also

Updated on May 26, 2022

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