Does anyone know how to calculate the slope of elliptical line by using the matlab？

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huazai2020
huazai2020 2020-7-8
评论： huazai2020 2020-7-12
I have some data of the elliptical line， does anyone know how to calculate the slope of elliptical line by using the matlab？
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James Tursa
James Tursa 2020-7-9
If you mean the slope of the tangent line at a point on the ellipse, take the differential of both sides:
2*x*dx/4 + 2*y*dy/16 = 0
Then solve for dy/dx, the slope of the tangent line at the point (x,y):
dy/dx = -4*x/y
John D'Errico
John D'Errico 2020-7-9
Or, given that equation, differentiate, recognizing that d/dx applied to x^2 is 2*x. d/dx applied to y^2 is 2*y*dy/dx. Now solve for dy/dx.

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Image Analyst
Image Analyst 2020-7-8
Exactly what is an "elliptical line"? That's a new one on me. I know lines, and I know ellipses, but not an elliptical line. What is it?
Anyway, if you have "some data" on a line, you can get the slope of a line fitted through your "some data" from the polyfit() function.
coefficients = polyfit(x, y, 1);
The slope of the line fitted through the x and y points is
slope = coefficients(1);
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Image Analyst
Image Analyst 2020-7-9
编辑：Image Analyst 2020-7-9
No, because I didn't know what you meant. So you have an ellipse and you want the slope of a line that's tangent to the ellipse at each points. What I'd probably do is Use John and James code. Untested code
slopeInfo = zeros(length(x), 3); % Col1 = x, col2 = y, col3 = slope
for k = 1 : length(x) % for every (x,y) point on the ellipse (almost)...
slopeInfo(k, 1) = x(k); % Assign x to column 1.
slopeInfo(k, 2) = y(k); % Assign y to column 2.
slopeInfo(k, 3) = -4 * x(k) / y(k); % Assign slope to column 3.
end

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