how to plot ellipse in this format?

I would like to ask how to plot ellipse in开发者_JS百科 such format:

ax^2+by^2+cxy+dx+ey-1=0

I tried with ezplot and contour and it didn't seem to work.

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If you use that equation you must satisfy the relation c^2 - 4ab < 0 for it to be an ellipse.

Edit: Also specifying more clearly how it does not seem to work (what you were expecting and what happened) could be useful.

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You need to use numeric values for the parameters a through e. Then you can plot the ellipse with ezplot.

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see this file on the matlab file exchange: ellipse.m