trend

Process Help

TREND - fit a polynomial trend surface to data

Process Name	Menu Path	Link to Command Table
TREND	Command line only	Click here

Introduction
Files, Fields and Parameters
Notes
Example
Errors

Introduction

Fits a polynomial trend surface to a set of data.

How to use

A polynomial of order 1, 2 or 3 may be fitted. The coefficients are calculated, displayed in the Command window, and stored in the output file. A summary of the goodness of fit parameters are also displayed in the Command window.

Files, Fields and Parameters

Input Files

Name	Description	I/O Status	Required	Type
IN	Input data file. Must contain the fields X , Y , and VALUE.	Input	Yes	Undefined

Output Files

Name	I/O Status	Required	Type	Description
OUT	Output	Yes	Undefined	Output file containing the surface coefficients. The fields are C0, CX, CY, CXY, CX2, CY2, CX2Y, CXY2, CX3, CY3.

Fields

Name	Description	Source	Required	Type	Default
X	X Co-ordinate fieldname.	IN	Yes	Numeric	Undefined
Y	Y Co-ordinate fieldname.	IN	Yes	Numeric	Undefined
VALUE	Field to be fitted.	IN	Yes	Numeric	Undefined

Parameters

Name	Description	Required	Default	Range	Values
ORDER	Order of surface (1,2, or 3).	Yes	1	1,3	1,2,3
PRINT	>0, displays original samples, fitted points and differences (0).	No	0	0,1	0,1
SELECT	Allows the user to select every nth record, where n=SELECT (1).	No	1	Undefined	Undefined

Notes

If any record has any of *X, *Y or *Z values absent, the record is ignored and is not included in the record count.

Example

!TREND

&IN(SAMPLES),&OUT(COEFFS),*X(XCOORD),
*Y(YCOORD),*VALUE(COPPER),@CINT=2.0,
@MINIMUM=0,@ORDER=2,@PRINT=1

Error and Warning Messages

Message	Description	Solution
>>> TOO MUCH DATA. COMPUTING TREND SURFACE ON FIRST 1000 RECORDS. <<<	The maximum number of points which may be processed is 1000. All other points are ignored, and processing continued with the first 1000.	Reduce the number of data points in the file.

>>> TOO LITTLE DATA. CANNOT COMPUTE TREND SURFACE OF REQUIRED ORDER. >>> ERR 120 <<< ( fileno) IN TREND	The minimum number of points needed for computation of a surface is 3 for order 1, 6 for order 2 and 10 for order 3. Fatal; the process is exited.	Specify an input file with sufficient data points.

>>> FIELD aaaaaaaa NOT NUMERIC <<< >>> ERR 120 <<< ( fileno) IN TREND	One of the X, Y or *Z fields were not numeric. Fatal; the process is exited.	Using the Datamine Table Editor, check the field types in the input data file.

>>>ORDER CANNOT BE LESS THAN ONE, ORDER = ONE HAS BEEN ASSUMED	A value of @ORDER below the minimum permitted value has been entered. The value is reset to the minimum and processing continues.	Specify a valid value for @ORDER.

>>>ORDER CANNOT BE GREATER THAN THREE. ORDER = THREE HAS BEEN ASSUMED	A value of @ORDER above the maximum permitted value has been entered. The value is reset to the maximum and processing continues.

>>>ABSOLUTE VALUE OF DIV. IS LESS THAN OR EQUAL TO ZERO >>> ERR 501 <<< ( 0) IN DSLE	The matrix of data presented for solution was singular. The data is inappropriate. Warning; the process continues, but the results may be meaningless.