TableInterpolation

(Function Library)

Description:	Given a graph described by a CSV file containing X and Y values, this function will interpolate a Y value for any provided X value within the range of the graph.
Returns:	Numeric
Usage:	Script or steady state.
Function Groups:	Oil & Gas
Related to:	ShellTemperatureCorrection
Format:	TableInterpolation(FileName, Input, Mode[, ErrorTag])
Parameters:

FileName

Required text. The path and name of the CSV file containing X and Y values for a graph.

Input

Required numeric. An X value, for which this function will return an interpolated Y value. This value must be within the range of X values found in the given CSV file.

Mode

Required numeric. Sets the type of interpolation to use.

Set to 0 for linear interpolation.

Set to 1 to return the Y value associated with the closest X value.

ErrorTag

Optional tag object. If provided, this must be an analog tag (typically an I/O tag in Analog mode). The value of that tag will be set according as follows:

Value	Meaning
0	Success
1	No file
2	Bad file (Includes a header or does not hold X,Y data points sorted by ascending X value .)
3	Input exceeds the maximum X value in the CSV file
4	Input is less than the minimum X value in the CSV file
5	Input value not provided
6	Mode not set to 0 or 1

Comments:

This function will read a table from a CSV file at the specified location and perform the selected type of interpolation for the Input value, returning the result. Returns Invalid if a result cannot be found.

Each line of the CSV file must contain two values: The X and Y coordinates for a point on the graph. No header should be included. The data must be sorted from top to bottom within the file in order by ascending X values.

An optional error tag can be provided for which an error value will be set.