NAG CL Interface
g03bdc (rot_​promax)

1 Purpose

g03bdc calculates a ProMax rotation, given information following an orthogonal rotation.

2 Specification

#include <nag.h>
void  g03bdc (Nag_RotationLoading stand, Integer n, Integer m, const double x[], Integer pdx, const double ro[], Integer pdro, double power, double fp[], Integer pdfp, double r[], Integer pdr, double phi[], Integer pdphi, double fs[], Integer pdfs, NagError *fail)
The function may be called by the names: g03bdc, nag_mv_rot_promax or nag_mv_promax.

3 Description

Let X and Y denote n by m matrices each representing a set of n points in an m-dimensional space. The X matrix is a matrix of loadings as returned by g03bac, that is following an orthogonal rotation of a loadings matrix Z. The target matrix Y is calculated as a power transformation of X that preserves the sign of the loadings. Let Xij and Yij denote the i,jth element of matrices X and Y. Given a value greater than 1 for the exponent p:
Yij = δij Xij p ,  
for
The above power transformation tends to increase the difference between high and low values of loadings and is intended to increase the interpretability of a solution.
In the second step a solution of:
XW=Y , X,Y n×m , ​ W m×m ,  
is found for W in the least squares sense by use of singular value decomposition of the orthogonal loadings X. The ProMax rotation matrix R is then given by
R=OW W~ , O, ​ W~ m×m ,  
where O is the rotation matrix from an orthogonal transformation, and W~ is a matrix with the square root of diagonal elements of WTW-1 on its diagonal and zeros elsewhere.
The ProMax factor pattern matrix P is given by
P = X W W~ , P n×m ;  
the inter-factor correlations Φ are given by
Φ= QT Q-1 , Φ m×m ;  
where Q=WW~; and the factor structure S is given by
S=PΦ , S n×m .  
Optionally, the rows of target matrix Y can be scaled by the communalities of loadings.

4 References

None.

5 Arguments

1: stand Nag_RotationLoading Input
On entry: indicates how loadings are normalized.
stand=Nag_RoLoadStand
Rows of Y are (Kaiser) normalized by the communalities of the loadings.
stand=Nag_RoLoadNotStand
Rows are not normalized.
Constraint: stand=Nag_RoLoadNotStand or Nag_RoLoadStand.
2: n Integer Input
On entry: n, the number of points.
Constraint: nm.
3: m Integer Input
On entry: m, the number of dimensions.
Constraint: m1.
4: x[n×pdx] const double Input
Note: the i,jth element of the matrix X is stored in x[i-1×pdx+j-1].
On entry: the loadings matrix following an orthogonal rotation, X.
5: pdx Integer Input
On entry: the stride separating matrix column elements in the array x.
Constraint: pdxm.
6: ro[m×pdro] const double Input
Note: the i,jth element of the matrix is stored in ro[i-1×pdro+j-1].
On entry: the orthogonal rotation matrix, O.
7: pdro Integer Input
On entry: the stride separating matrix column elements in the array ro.
Constraint: pdrom.
8: power double Input
On entry: p, the value of exponent.
Constraint: power>1.0.
9: fp[n×pdfp] double Output
Note: the i,jth element of the matrix is stored in fp[i-1×pdfp+j-1].
On exit: the factor pattern matrix, P.
10: pdfp Integer Input
On entry: the stride separating matrix column elements in the array fp.
Constraint: pdfpm.
11: r[m×pdr] double Output
Note: the i,jth element of the matrix R is stored in r[i-1×pdr+j-1].
On exit: the ProMax rotation matrix, R.
12: pdr Integer Input
On entry: the stride separating matrix column elements in the array r.
Constraint: pdrm.
13: phi[m×pdphi] double Output
Note: the i,jth element of the matrix is stored in phi[i-1×pdphi+j-1].
On exit: the matrix of inter-factor correlations, Φ.
14: pdphi Integer Input
On entry: the stride separating matrix column elements in the array phi.
Constraint: pdphim.
15: fs[n×pdfs] double Output
Note: the i,jth element of the matrix is stored in fs[i-1×pdfs+j-1].
On exit: the factor structure matrix, S.
16: pdfs Integer Input
On entry: the stride separating matrix column elements in the array fs.
Constraint: pdfsm.
17: fail NagError * Input/Output
The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

NE_ALLOC_FAIL
Dynamic memory allocation failed.
NE_INT
On entry, m=value.
Constraint: m1.
On entry, pdfp=value.
Constraint: pdfp>0.
On entry, pdfs=value.
Constraint: pdfs>0.
On entry, pdphi=value.
Constraint: pdphi>0.
On entry, pdr=value.
Constraint: pdr>0.
On entry, pdro=value.
Constraint: pdro>0.
On entry, pdx=value.
Constraint: pdx>0.
NE_INT_2
On entry, n=value and m=value.
Constraint: nm.
On entry, pdfp=value and m=value.
Constraint: pdfpm.
On entry, pdfs=value and m=value.
Constraint: pdfsm.
On entry, pdphi=value and m=value.
Constraint: pdphim.
On entry, pdr=value and m=value.
Constraint: pdrm.
On entry, pdro=value and m=value.
Constraint: pdrom.
On entry, pdx=value and m=value.
Constraint: pdxm.
NE_INTERNAL_ERROR
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
NE_REAL_ARG_LE
On entry, power=value.
Constraint: power>1.0.
NE_SVD_FAIL
SVD failed to converge.

7 Accuracy

The calculations are believed to be stable.

8 Parallelism and Performance

g03bdc is threaded by NAG for parallel execution in multithreaded implementations of the NAG Library.
g03bdc makes calls to BLAS and/or LAPACK routines, which may be threaded within the vendor library used by this implementation. Consult the documentation for the vendor library for further information.
Please consult the X06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this function. Please also consult the Users' Note for your implementation for any additional implementation-specific information.

9 Further Comments

None.

10 Example

This example reads a loadings matrix and calculates a varimax transformation before calculating P, R and σ for a ProMax rotation.

10.1 Program Text

Program Text (g03bdce.c)

10.2 Program Data

Program Data (g03bdce.d)

10.3 Program Results

Program Results (g03bdce.r)