Linear int

LINEAR_INT

Type	Function
Input X	REAL (input)
XY	ARRAY [1..20,0..1] (Ascending sorted values pairs)
PTS	INT (number of pairs of values)
Output	REAL (output)
	LINEAR_INT is a linear interpolation module. A characteristic is described by a maximum of 20 coordinate values (X, Y) and is cut up to 19 linear segments. The definition of the coordinate values is passed in an array which describes the characteristic with individual X, Y describes value pairs. The value pairs must be sorted by the x_value. If an X value is called outside range which is described by the value pairs, then the first respective last linear segment is extrapolated and the corresponding value Issued. To keep the number of definition points flexible, at the input PTS is given the number of points. The possible score is in the range from 3 to 20, wherein each individual dot is shown with X-and Y-value.

Example:

VAR EXAMPLE : ARRAY[1..20,0..1] := -10,-0.53, 10,0.53, 100,88.3, 200,122.2; END_VAR

for the above definition, the following results are valid: LINEAR_INT (0, EXAMPLE, 4) = 0; LINEAR_INT (30.0, EXAMPLE, 4) = 20.0344; LINEAR_INT (66.41, EXAMPLE, 4) = 55.54229; LINEAR_INT (66.41, EXAMPLE, 4) = 55.54229;