Ellipse in PCA with parameters "a" and "b"defined.
On 01/22/2013 11:12 AM, mary wrote:
Hi, I have to construct an ellipse interval region on a PCAbiplot, I have my parameters "a" and "b" and I would apply the formula: draw.ellipse(x, y, a = , b = ) I have done a PCA on my data so I have my scores and loading for the first and second component, but my answer is what I have to choose as X and Y into the formula? if "a" and "b" are scalars or vectors should be x and y scalars or vectors too?
Hi Mary, If this is draw.ellipse from the plotrix package, there should be an x and y corresponding to each pair of a and b. I was unable to work out which PCA biplot function you are using, so I am not sure whether the plots are drawn in base graphics. If not, you might have some problems with the x and y coordinates. Jim