region.confi.smooth Function (GPL)

Syntax

region.confi.smooth.<smooth function>(<algebra>, <function>)

<algebra>. Graph algebra, such as x*y. Refer to Brief Overview of GPL Algebra for an introduction to graph algebra.

<smooth function>. The smooth function for which to calculate the confidence interval. Valid values are cubic, linear, and quadratic.

<function>. One or more valid functions. These are optional. If no alpha function is specified, 0.95 is used for the alpha.

Description

Calculates the confidence interval around a smoother function. The function creates two values. When using the interval, area, or edge graphic elements, this function results in one graphic element showing the range of the confidence interval. All other graphic elements result in two separate elements, one showing the confidence interval below the smoother function and one showing the confidence interval above the smoother function.

Examples

Figure 1. Example: Showing the confidence interval around a fit line

ELEMENT: line(position(region.confi.smooth.linear(salbegin*salary)))