Equivalent ellipse of a set of points.

   ELL = equivalentEllipse(PTS);
   Computes the ellips with the same moments up to the second order as the
   set of points specified by the N-by-2 array PTS.

   The result has the following form:
   ELL = [XC YC A B THETA],
   with XC and YC being the center of mass of the point set, A and B being
   the lengths of the equivalent ellipse (see below), and THETA being the
   angle of the first principal axis with the horizontal (counted in
   degrees between 0 and 180 in counter-clockwise direction). 
   A and B are the standard deviations of the point coordinates when
   ellipse is aligned with the principal axes.

   Example
     pts = randn(100, 2);
     pts = transformPoint(pts, createScaling(5, 2));
     pts = transformPoint(pts, createRotation(pi/6));
     pts = transformPoint(pts, createTranslation(3, 4));
     ell = equivalentEllipse(pts);
     figure(1); clf; hold on;
     drawPoint(pts);
     drawEllipse(ell, 'linewidth', 2, 'color', 'r');

   See also
     ellipses2d, drawEllipse, equivalentEllipsoid, principalAxes,
     principalAxesTransform 

Package: matgeom