Find intersection between two curves

Hello i have plot two curves and i would like to create a function so as to find the intersections between the two curves

Here is my code :

x=-100*pi:pi/32:100*pi;
y1=exp(x);
y2=sin(x);

figure(1)
plot(y1,'b');hold on
plot(y2,'g');
hold off
grid

Answer 1

[Jan]

The intersection is the location, where both functions have the same value. Then their difference is 0.

You can use fzero with the function: @(x) exp(x) - sin(x).

[Akash Gooljar]

Hello sir , thank you for the detailed explanations i did try but did not got the intersections

[Jan]

Please post the code you have tried and explain, what "did not get" mean.

What is a meaningul range for searching for intersections? exp(x) is growing very fast, while sin(x) lives inside [-1, +1]. So maybe:

x  = linspace(-4*pi, pi, 1000);
y1 = exp(x);
y2 = sin(x);
figure
plot(x, y1, 'b', x, y2, 'g');

Then you could start the search for the zeros of @(x) exp(x) - sin(x) at e.g. -3 - these are the two inputs for fzero().

[Akash Gooljar]

x = linspace(-4*pi, pi, 1000);

y1 = exp(x);

y2 = sin(x);

figure

plot(x, y1, 'b', x, y2, 'g');

x1=y1 -y2;

fzero = (x1,-3);

[Akash Gooljar]

i did try it like this,but im getting some errors

[Jan]

Please post the error message, if you mention an error.

fzero is a function. You have to provide a function as 1st input:

fzero(@(x) exp(x) - sin(x), -3)

[Jan]

@Star Strider: What a pitty that you have deleted your answer. It was a valuable addition to my answer: You have considered the situation, that the input data are provided as vectors, while I suggested a method, when they are functions.

If somebody searchs in the forum for "intersection between two curves", your answer might have been more suiting then my one.

Your answers are too valuable to be deleted. They are useful and do not impede the readers.

I thought of unselecting my answer and accepting yours to keep it in the forum. But this cannot be a general strategy.

[ANA MARIA SANCHEZ GONZALEZ]

Hi guys! I need to find the intersection between two curves but one of them is given as vectors (experimental data). Could you please help me with that? Thank you in advance!

[Torsten]

Is interpolating the measurement data by a spline curve, taking the difference of the two so created curves and searching for a zero of this difference function an option ?

% Artificial measurement data
x = 0:0.1:2;
fi_measurement = x.^2;
% Second curve
f = @(x) x;
% Fit measurement data by spline curve
f_measurement = @(xq) interp1(x,fi_measurement,xq,'spline');
% Find intersection(s) between spline curve and second curve
sol1 = fzero(@(x)f(x)-f_measurement(x),0.5)

sol1 = -1.0469e-22

sol2 = fzero(@(x)f(x)-f_measurement(x),1.5)

sol2 = 1