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

I have some data of the elliptical line， does anyone know how to calculate the slope of elliptical line by using the matlab？

[John D'Errico]

Do you have the equation of the ellipse?

[huazai2020]

x^2/4+y^2/16=1

[James Tursa]

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]

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.

Answer 1

[Image Analyst]

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);

[huazai2020]

The elliptical line is equal to the ellipse in my meaning. What does the coefficients(1) mean?

[madhan ravi]

Didn’t you read his comment:

” The slope of the line fitted through the x and y points is” ?

[huazai2020]

As you see the below codes, but it only give one slope,not all the slope on each point, how to solve it ?

clc;

clear all;

rgx = '([-+]?\d+\.?\d*([eE][-+]?\d+)?)';

str = fileread('xcood-011.out');

tkn = regexp(str,[rgx,'\s+',rgx],'tokens');

walldata(:,1:2) = str2double(vertcat(tkn{:}));%21为壁面x值，22为壁面y值

x=walldata(:,1);%提取壁面x坐标

y=walldata(:,2);%提取壁面y坐标

coefficients = polyfit(x, y, 1);

slope = coefficients(1);

[Image Analyst]

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

[huazai2020]

But how can I import the data to x（k）？