The code(given) only store last points of intersection.How to store all points of intersection?

      % code
  %%%%Determine point of intersection between perpendicular lines(from curve
  %%%%2) and curve 1%%%%%%%%%

clear all; clc;
Y= [318  318  317  317  317  317  317  318  318  319  320  320  320  321  321  321  320  320  320  320  318  318  318  318  318  318];
X = [322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347];

Y1 = [338 338  338  338  338  338  339  339  339  339  339  339  339  339  339  339  339  339  340  340  340  340  340  340  340  340];

   for i=1:length(X)
       X0 = X(i); %%%%columnwise%%%%%%

   n = 100; % 100 or some higher number for nice curves
   f = 0.1; % this defines the length of the tangent
  x = linspace(min(X),max(X),n); 

y2 = interp1(X,Y1,x,'spline');%%%%for smooth curve 1

y = interp1(X,Y,x,'spline'); %%%%for smooth curve 2

xt = X0+(f*(max(X)-min(X))*[-1 0 1]);%%%x coordinates of tangent 

m = diff(y)./diff(x);%%%%calculate the slope of the tangent

m = [m, m(end)]; % so just add one at the end

k = min([find(x >= X0,1,'first'), length(x)]);

yt = y(k) + m(k)*(0.1*(max(X)-min(X))*[-1 0 1]);%%%%y coordinates of tangent

%%%%%%%plot normal to the tangent%%%%%5
A=[xt(:,1),yt(:,1)];

B=[xt(:,3),yt(:,3)];

null(A-B);

xa = [A(:,1), B(:,1)];

ya = [A(:,2),B(:,2)];

gg=1.5*(max(Y1)-min(Y));% this defines the length of the normal

normal = [mean(xa),mean(ya)] + gg*null(A-B)';

line([mean(xa),normal(1)],[mean(ya),normal(2)],'color','r','LineWidth',2);

%%%Determine point of intersection of perpendicular lines (from curve2) and curve 1

   v1=[mean(xa),normal(1,1)];v2=[mean(ya),normal(1,2)];%%%Points that represents perpedicular lines

[x0,y0,iout,jout] = intersections(v1,v2,x,y2);

plot(X,Y,'ro', x,y,'b',xt,yt,'--g',x,y2,'b');  hold on;
plot(x0,y0,'bo')
 end
 %%%%%%%%Main aim is to determine max & min distance between two curves.

[vaishali]

please help to come out from this problem

Answer 1

[Geoff Hayes]

If there is a (for or while) loop that is calculating a particular value at each iteration and you want to save that value, then you will need to store the result in a matrix or cell array. I'm going to suggest the latter in this case to handle the fact that the returned vectors from intersections may be of different size (or empty) at each iteration.

The first thing you need to do is define your cell array which you will do outside of the for loop. Since you know the number of iterations, then you can set the size of the array

 n = length(X);
 intersectionPoints = cell(n,1);

Now start the work

 for i=1:n
       X0 = X(i); %%%%columnwise%%%%%%

       % etc.

Once you have calculated the intersection points, save them to the cell array

       [x0,y0,iout,jout] = intersections(v1,v2,x,y2);

       % save x0 and y0
       intersectionPoints{i} = [x0 y0];  % I'm assuming that x0 and y0 are column vectors

And that is it. Once the loop ends, the intersectionPoints cell array has all intersection points (if they exist) for each iteration of the loop.

Try the above and see what happens!

[vaishali]

Now want to calculate distance between starting points and the intersection point(end Points).please help to come out from this problem.

[Geoff Hayes]

If the starting point is given by (x0,y0) and the end point is given by (x1,y1), then the Euclidean distance between the two points is

 dist = sqrt((x0-x1)^2 + (y0-y1)^2);

You will have to write code to iterate over each starting point and end (intersection) point pair and compute the above distance value.

[vaishali]

Got it. Thank you very much sir

[Geoff Hayes]

Awesome!