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Fabian
Posts:
22
Registered:
8/4/08


Re: rotated ellipse in cartesian coordinates
Posted:
Dec 9, 2008 7:26 PM


"Adam" <not.real@email.com> wrote in message <ghlr2i$mi9$1@fred.mathworks.com>... > "Fabian" <fabian.conrad@gmx.de> wrote in message <ghl5o5$29q$1@fred.mathworks.com>... > > I've got a matlab procedure that fits an ellipse to a set of points, my problem is that I only need a certain x range and xstep in cartesian coordinate system. Can somebody help me with a formula for y as a function of x and my ellipse (defined by [z, a, b, alpha] returned by fitellipse:) > > %parameterised by 0 <= theta < 2*pi is: > > X = Z + Q(alpha) * [a * cos(theta);b * sin(theta)] > > Does it have to be x and y? That would be awkward. > > http://en.wikipedia.org/wiki/Ellipse > > Parametric form of an ellipse rotated counterclockwise by an angle k > > x = h + a * cos(t) * cos(k)  b * sin(t) * sin(k) > y = k + b * sin(t) * cos(k) + a * cos(t) * sin(k) > > ~Adam I need y for a certain range of xvalues so it has to be x and y, is there a way?



