How to find the intersection values of line and curve?

How to find the intersection values of line(black) and the curve(blue). And I need the intersection points in ascending order in array. Can you please help.....

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% This is a program for 1-D Photonic crystal
% For Photonic band structure calculation and Transmission Spectrum
% This program uses Transfer Matrix Method
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clc
clear all
close all
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Initialization of parameters
dB=7778e-9;                         % Thickness of Second Layer
dA=0.1*5303e-9;                         % Thickness of First Layer

nA=3.3;                             % Refractive index of First Layer
nB=2.25;                            % Refraive index of Second Layer
n0=1;                               % Refractive index of Incident and transmission medium
c=3e8;                              % Velocity of Light (m/s)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Frequency Range
frequncy=0.1:0.1:40;                    % Frequncy in THz
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
for loop=1:length(frequncy)
    % angular frequency
    w=2*pi*frequncy*1e12;
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    d=dA+dB;    DA=((w(loop))/c)*dA*nA;    DB=((w(loop))/c)*dB*nB;
    m11=cos(DA);   m12=-1i*sin(DA)/nA;   m21=-1i*nA*sin(DA);   m22=cos(DA);   mA=[m11 m12; m21 m22];
    l11=cos(DB);   l12=-1i*sin(DB)/nB;   l21=-1i*nB*sin(DB);   l22=cos(DB);   mB=[l11 l12; l21 l22];
      m=(mA*mB);
    RHS(loop)=(m(1,1)+m(2,2))/2;
 
end
plot(frequncy,RHS)
hold on
yline(-1)
yline(1)
hold off

[Bruno Luong]

What is the difference with your question previously asked here?

[GULZAR]

Sorry i'm new in matlab. Here i'm using for loop. I'm confusing to use that previous method.

[Dyuman Joshi]

"Here i'm using for loop."

That does not make any difference.

You can still apply the method suggested in that answer.

"I'm confusing to use that previous method. "

How are you confused?

[Bruno Luong]

If you are confused the iI recommend asking specific question focusing on what confuses you, instead of ignoring it and ask again the same question. You'll end of with a tone of things that confuse you even after 10 year of MATLAB practicing.

Answer 1

[Bruno Luong]

OK I'll be nice with you because of your laziness I just copy the solution of another thread here; wirh a little adaptation to sort them

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% This is a program for 1-D Photonic crystal
% For Photonic band structure calculation and Transmission Spectrum
% This program uses Transfer Matrix Method
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%clc
%clear all <====== BAD programming practice
%close all
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Initialization of parameters
dB=7778e-9;                         % Thickness of Second Layer
dA=0.1*5303e-9;                         % Thickness of First Layer

nA=3.3;                             % Refractive index of First Layer
nB=2.25;                            % Refraive index of Second Layer
n0=1;                               % Refractive index of Incident and transmission medium
c=3e8;                              % Velocity of Light (m/s)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Frequency Range
frequncy=0.1:0.1:40;                    % Frequncy in THz
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
for loop=1:length(frequncy)
    % angular frequency
    w=2*pi*frequncy*1e12;
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    d=dA+dB;    DA=((w(loop))/c)*dA*nA;    DB=((w(loop))/c)*dB*nB;
    m11=cos(DA);   m12=-1i*sin(DA)/nA;   m21=-1i*nA*sin(DA);   m22=cos(DA);   mA=[m11 m12; m21 m22];
    l11=cos(DB);   l12=-1i*sin(DB)/nB;   l21=-1i*nB*sin(DB);   l22=cos(DB);   mB=[l11 l12; l21 l22];
      m=(mA*mB);
    RHS(loop)=(m(1,1)+m(2,2))/2;
 
end

allyx = [-1 1];
xintersect = [];
yintersect = [];
for yx = allyx
    ys = RHS-yx;
    i = find(ys(1:end-1).*ys(2:end) <= 0);
    % linear interpolation
    i1 = i; ss1 = ys(i1);
    i2 = i1 + 1; ss2 = ys(i2);
    w = ss2./(ss2-ss1);
    xx = w.*frequncy(i1) + (1-w).*frequncy(i2);
    yy = yx+zeros(size(xx));
    xintersect = [xintersect, xx];
    yintersect = [yintersect, yy];
end
[xintersect, is] = sort(xintersect);
yintersect= yintersect(is);

figure
plot(frequncy,RHS)
hold on
yline(allyx)
plot(xintersect, yintersect, 'or')
hold off

Answer 2

[Rawad SADAH]

Try this code

% Finding intersection points
threshold = 0.01;  % Adjust this threshold based on your data and precision needs
intersection_points = [];
for loop = 2:length(frequncy)
    if (RHS(loop) > -1 && RHS(loop - 1) < -1) || (RHS(loop) < 1 && RHS(loop - 1) > 1)
        % Perform linear interpolation to find the approximate intersection point
        t = (1 - RHS(loop - 1)) / (RHS(loop) - RHS(loop - 1));
        intersection_freq = frequncy(loop - 1) + t * (frequncy(loop) - frequncy(loop - 1));
        
        % Add the intersection point to the array
        intersection_points = [intersection_points, intersection_freq];
    end
end

% Sort the intersection points in ascending order
sorted_intersection_points = sort(intersection_points);

disp("Intersection Points:");
disp(sorted_intersection_points);

% Plotting the intersection points on the blue curve
hold on;
plot(sorted_intersection_points, ones(size(sorted_intersection_points)), 'ro');
hold off;

[GULZAR]

It doesn't work.