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# principal_axis

## PURPOSE PRINCIPAL_AXIS - Finds principal axis of each grid point.

## SYNOPSIS function [a, LL] = principal_axis( h )

## DESCRIPTION ``` PRINCIPAL_AXIS - Finds principal axis of each grid point.

Usage: [angles, variances] = principal_axis( hfrc_obj )

This function returns the direction of the principal axis (in radians)
of each grip point of the HFRC object.  It removes bad data before
doing the calculation.  The mean of each series is also removed before
calculation.

It will also optionally return the variances explained by the major and
minor axes.

The negative of the angles returned can be used in rotate to place each
series on it's principal axis.

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\$Id: principal_axis.m,v 1.1 2003-06-04 00:40:04 dmk Exp \$

Copyright (C) 2001 David M. Kaplan

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## CROSS-REFERENCE INFORMATION This function calls:
• EOF EOF - computes EOF on a field of an HFRC object.
• end END - basic end method for HFRC objects.
• gooddata GOODDATA - returns a matrix of good data in object.
• isempty
• polyfit POLYFIT - Polynomial fitting for HFRC objects.
• polyval POLYVAL - HFRC method for polyval function
• size SIZE - returns [ (num times), (num gridpts) ].
• EOF EOF - computes EOF of a matrix.
This function is called by:
• summary SUMMARY - Make summaries of HFRC objects.

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