参考Wikipedia:

x(theta) = a0 + ax*sin(theta) + bx*cos(theta)
y(theta) = b0 + ay*sin(theta) + by*cos(theta)

翻译成MATLAB版本。

calculateEllipse.m：

function [X Y] = calculateEllipse(x, y, a, b, angle, steps)
    %# This functions returns points to draw an ellipse
    %#
    %#  @param x     X coordinate
    %#  @param y     Y coordinate
    %#  @param a     Semimajor axis
    %#  @param b     Semiminor axis
    %#  @param angle Angle of the ellipse (in degrees)
    %#

    error(nargchk(5, 6, nargin));
    if nargin<6, steps = 36; end

    beta = -angle * (pi / 180);
    sinbeta = sin(beta);
    cosbeta = cos(beta);

    alpha = linspace(0, 360, steps)' .* (pi / 180);
    sinalpha = sin(alpha);
    cosalpha = cos(alpha);

    X = x + (a * cosalpha * cosbeta - b * sinalpha * sinbeta);
    Y = y + (a * cosalpha * sinbeta + b * sinalpha * cosbeta);

    if nargout==1, X = [X Y]; end
end

样例：

p = calculateEllipse(0, 0, 20, 10, 50);
plot(p(:,1), p(:,2), '.-'), axis equal