ELLIPSATE

circumscribe data into an ellipse

Syntax: [ ellipseX , ellipseY ] = ellipsate( dataX , dataY , stdev )

Example:
data=mvnrnd([0.5 1.5], [0.025 0.03 ; 0.03 0.16], 100);
dataX=data(:,1);
dataY=data(:,2);
stdev = 2; %# 2 standard deviations, 95% of population
[ ellipseX , ellipseY ] = ellipsate( dataX , dataY , stdev );
plot(dataX, dataY, '.')
axis square
hold on
plot(ellipseX , ellipseY, 'r')

Function based on the code of Amro, described in
http://stackoverflow.com/questions/3417028/ellipse-around-the-data-in-matlab