Process Help

FACTOR - R-mode factor analysis

 

Process Name

Menu Path

Link to Command Table

FACTOR

Sample Analysis ribbon | Geochemical Processes | R Mode Factor Analysis

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Introduction

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

R - mode factor analysis using the un-rotated, 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.

How to use

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.

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.

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

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

Second field to be used.

IN

No

Numeric

Undefined

F3

Third field to be used.

IN

No

Numeric

Undefined

F4

Fourth field to be used.

IN

No

Numeric

Undefined

F5

Fifth field to be used.

IN

No

Numeric

Undefined

F6

Sixth field to be used.

IN

No

Numeric

Undefined

F7

Seventh field to be used.

IN

No

Numeric

Undefined

F8

Eighth field to be used.

IN

No

Numeric

Undefined

F9

Ninth field to be used.

IN

No

Numeric

Undefined

F10

Tenth field 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.

No

0

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.

No

1

Undefined

Undefined

NUMEIGEN

 

Option

Description

(0)

Maximum number of eigenvalues is set to the number of fields or to 10, whichever is the lower.

No

0

Undefined

Undefined

PROMAXCF

 

Option

Description

(3)

Promax oblique rotation exponent. Range is 1-9.

No

3

1,9

Undefined

PRINT

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

No

0

0,1

0,1

Notes

There is currently a restriction of 45 variables. There is no limit on the number of samples.

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

Solution

*** 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.