FACTOR Process

To access this process:

Sample Analysis ribbon >> Geochemical Processes >> R Mode Factor Analysis.
Enter "FACTOR" into the Command Line and press <ENTER>.
Display the Find Command screen, locate FACTOR and click Run.

See this process in the Command Table.

Process Overview

Define a number of factors from the common inter-correlation between variables using the correlation (R) matrix.

R - mode factor analysis using the unrotated, varimax and promax rotated correlation matrix to classify variables into groups (factors) and calculate factor scores. This defines a number of factors from the common inter-correlation between variables using the correlation (R) matrix.

Note the difference from the principal components analysis which uses variance. The number of factors selected is usually less than the number of variables. Three types of factor loadings are calculated, a) the un-rotated solution, ie principal components, b) the rotated varimax solution and c) the oblique promax solution.

Statistical factor analysis is completed by iterative calculation of the un-rotated factor matrix. Non- statistical factor analysis is completed by a single pass only, ie. the varimax and promax rotations are non statistical. The number of factors selected can be forced by defining a given eigen value or a given number of factors. Significance levels are calculated using the Burt-Banks equation.

FACTOR and PCA Processes

Note the difference from the principal components analysis calculation, which uses variance.

The number of factors selected is usually less than the number of variables. Three types of factor loadings are calculated, a) the un-rotated solution, ie principal components, b) the rotated varimax solution and c) the oblique promax solution. Statistical factor analysis is completed by iterative calculation of the un-rotated factor matrix. Non- statistical factor analysis is completed by a single pass only, ie. the varimax and promax rotations are non statistical. The number of factors selected can be forced by defining a given eigen value or a given number of factors. Significance levels are calculated using the Burt-Banks equation.

File Handling

The input data file (&IN) must have sample identifier field (@SAMPID) which has to be declared on input. Optional output files, for un-rotated (&SCORES), rotated (RSCORES) and oblique rotated (&OSCORES) are available for farther processing.

If the user wishes to plot maps of the output scores then the scores files can be joined to the original input file using the JOIN process and defining SAMPID as the keyfield.

Note: There is a limit of 45 variables. There is no limit on the number of samples.

Input Files

Name	Description	I/O Status	Required	Type
IN	Input file.	Input	Yes	Undefined

Output Files

Name	I/O Status	Required	Type	Description
USCORES	Output	No	Undefined	Optional output file for unrotated factor scores.
RSCORES	Output	No	Undefined	Optional output file for varimax factor scores.
OSCORES	Output	No	Undefined	Optional output file for promax factor scores.

Fields

Name	Description	Source	Required	Type	Default
SAMPID	Field containing sample identification	IN	Yes	Any	Undefined
F1	First field to be used. No fields specified means all.	IN	No	Numeric	Undefined
F2-F10	Second and subsequent fields to be used.	IN	No	Numeric	Undefined

Parameters

Name

Description

Required

Default

Range

Values

MAXIT

Number of iterations required, valid only for the unrotated PCA option in factor analysis. =(0) Non statistical factor analysis. =10 Maximum number of iterations allowed for statistical factor analysis.

0,10

0,1,2,3,4,5,6,,7,8,9,10

EIGENMIN

Option	Description
(1)	Eigenvalue required to select the number of components.

Undefined

NUMEIGEN

Option	Description
(0)	Maximum number of eigenvalues is set to the number of fields or to 10, whichever is the lower.

Undefined

PROMAXCF

Option	Description
(3)	Promax oblique rotation exponent. Range is 1-9.

1,9

Undefined

> 0 Display scores on the screen (0). Note - Do not use for large files.

0,1

Example

!FACTOR &IN(SEDDET),&USCORES(USCORES),&OSCORES(OSCORES),
@SAMPID='ID',@MAXIT=0,@EIGENMIN=1,@NUMEIGEN=0,
@PROMAXCF=3,@PRINT= 0

Error and Warning Messages

Message	Description
* Warning * GROUPID field has more than three words. Only the first 3 will be used.
>>> ERR 122 <<< ( fileno.) IN FACTOR	No numeric fields on file (filename)
>> ERR 120 <<< ( fileno.) IN FACTOR	Compulsory file, field or parameter missing.
* Error * Failure in matrix inversion, check data.
* Error * Failure in inversion during oblique rotation, check data.