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POLREG - calculate polynomial regression coefficients

 

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Link to Command Table

POLREG

Sample Analysis ribbon | Statistics Processes | Polynomial Regression

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Introduction

Polynomial regression. The polynomial fitted is up to the 5th order, and thus includes a regression line.

How to use

The polynomial is of the form:-

Y = C0 + C1*X + C2*X2 + C3*X3 + C4*X4 + C5*X5

where the coefficients C0, C1, C2, C3, C4 and C5 are written to the output file.

The input file must contain two explicit numeric fields *X and *Y. The polynomial is calculated as Y estimates for X values. There must be at least (order+1) points. If either the *X or *Y value is absent data in a particular record, the record is ignored. This allows regression polynomials to be computed on incomplete sets of data; for example original assays and a partial set of check assays.

DATAFILE: Name of the input data file.
XDATA: The X field in the input file that was used.
YDATA: The Y field in the input data file that was used.
GOODNFIT: The goodness of fit.
CORRCOEF: The coefficient of variance.
STDERR: The standard error.


Files, Fields and Parameters

Input Files

Name

Description

I/O Status

Required

Type

IN

Input file.

Input

Yes

Undefined

Output Files

Name

I/O Status

Required

Type

Description

OUT

Output

No

Undefined

Output file containing the coefficients.

Fields

Name

Description

Source

Required

Type

Default

X

X co-ordinate of the sample data.

IN

Yes

Numeric

X

Y

Y co-ordinate of the sample data.

IN

Yes

Numeric

Y

Parameters

Name

Description

Required

Default

Range

Values

ORDER

Order of the polynomial required (1,2,3,4 or 5).

Yes

1

1,5

1,2,3,4,5

PRINT

If set to 1 then a table of estimated values, based on the regression equation, will be written to the Command window.  The default is (0), do not create the table.

No

0

0,1

0,1


Notes

No additional notes.


Example

In the following example, a regression line is calculated for estimating P2O5 field values from  FE field values in file assays.

!POLREG     &IN(ASSAYS),&OUT(COEFFS),*X(FE),*Y(P2O5),@ORDER=1
 


Error and Warning Messages

Message

Description

Solution

>>> ORDER CANNOT BE LESS THAN 1, ORDER=1 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.

 

 

 

 

>>> ORDER CANNOT BE GREATER THAN 5, ORDER=5 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.

 

 

 

 

>>> FIELD nnnnnnnn IS NOT NUMERIC <<<

>>> ERR 120 <<< ( fileno) IN POLREG

Either the *X or *Y fields were not numeric. Fatal; the process is exited.

 

 

 

 

>>> TOO LITTLE DATA, CANNOT COMPUTE POLYNOMIAL OF REQUIRED ORDER <<<

>>> ERR 120 <<< ( fileno) IN POLREG

The minimum number of points required is @ORDER + 1. Fatal; the process is exited.

 

 

 

 

>>> 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.