how to mark and print the intersecting coordinates of two lines

I have x1,y1 and x2, y2 data sets that give me two lines graphs.

I want to find the intersecting point of these two lines and and print it on the graph.

I tried following different functions like intesect but did not work.

Could someone please help me with this?

[Matt J]

Since it is discrete data, you need a more formal definition of what it means for them to "intersect". Suppose we have

[x1,y1,x2]=deal([0,1]);
y2=[1,0];

plot(x1,y1,'--x', x2,y2,'-o')

These seem to intersect at (x,y)=[0.5,0.5] but only because I've chosen to connect the points with straight lines instead of some other kind of connecting curve. Is that what you want?

[Anitha Limann]

Yes. i have these datasets

x1=[10,20,30,40,50,75,100,125,150,175,200,225,250,275];

t1=[1.6,3.2,4.8,6.4,8,12,16,20,24,28,32,36,40,44];

x2=[150,175,200,225,250,275,300,325,350,375,400];

t2=[26.62,29.69,32.75,35.82,38.89,41.96,45.02,48.09,51.16,54.23,57.29];

some point values. where i get this graph

so i want to find this intersecting point and print it on the graph.

Answer 1

[Star Strider]

Much depends on what ‘x1’, ‘y1’ and the rest are.

One approach (sssuming multiple intersections, although thiis will also work for only one intersection) would be —

x1 = linspace(-2, 15);
y1 = 2 + 3*x1;
x2 = linspace(-10, 10);
y2 = (x2-2).^2;

xq = linspace(min([x1,x2],[],2), max([x1,x2],[],2));            % Create Common 'x' Vector
y1q = interp1(x1, y1, xq, 'pchip','extrap');                    % Interpolate To It
y2q = interp1(x2, y2, xq, 'pchip','extrap');                    % Interpolate To It
idx = find(diff(sign(y1q-y2q)));                                % Approximate Indices Of Intersections
for k = 1:numel(idx)
    idxrng = max(1,idx(k)-2) : min(numel(xq),idx(k)+2);         % Index Range
    xi(k) = interp1(y1q(idxrng)-y2q(idxrng), xq(idxrng), 0);    % Interpolate X-Intersection
    yi(k) = interp1(xq(idxrng), y1q(idxrng), xi(k));            % Interpolate Y-Intersection (Either Y-Vector Will Work)
end
Intercepts = [xi; yi]

Intercepts = 2×2

0.3001 6.7004 2.9004 22.1012

figure
plot(x1, y1)
hold on
plot(x2, y2)
plot(xi, yi, '+r', 'MarkerSize',10)
hold off
grid
legend('y1','y2','Intersections', 'Location','best')

Experiment to get the desired result.

.

[Anitha Limann]

Thank you so much it worked well.

[Star Strider]

As always, my pleasure!

.