Finding the endpoint (tip) in a figure

Hello Matlab Community,

As shown, this is a figure i generated using matlab. I want to obtain only the endpoints(in red dot) of the figure. Then use the obtain points to plot dotted points.

I tried using the findpeak function but i realized certain endpoints of the values are missing and i couldnot find the points either.

Thanking you in advance

Answer 1

[Fangjun Jiang]

It looks like the figure is created by using stem(). If you created the figure, won't you have the data for the "red dot" already?

x=0:0.1:2*pi;
y=sin(x);
stem(x,y,'MarkerFaceColor','red')

[Evans Gyan]

Thank you for your answer but actually this is how the figure looks.

Assuming we have the code

x=0:0.1:2*pi;

y = diric(2*pi*x,5);

figure;stem(x,y,'MarkerFaceColor','red') % this display the red dot at the apex

figure;plot(x,y1) %this display the plot.

How do I obtain the endpoint (tip or the highest point) of each sinc wave.

[Fangjun Jiang]

what is y1? Is it a typo and should be y? Are you looking for plot(x,y,'o')?

[Evans Gyan]

Sorry, y1 is a typo. It should be y. A plot of (x,y,'o') is also a great idea but I only need the apex points or the highest point

[Fangjun Jiang]

findpeaks() is the right function to use. You may need to play with the arguments.

[Evans Gyan]

Thank you Fangjun for your response. I finally managed to get it working. This is how i code it

x=0:0.1:2*pi;
y = diric(2*pi*x,5);                                       
n = 6;  % define the no of interval for division
nopts= fix(size(x,2)/n);    % neccessary no of apex (tip) points
l = 1;
for jj = 1:n:size(x,2)-n    
[h(l) inx] = max(y(1,jj:n+jj));
c = jj:n+jj;
c1(l) = c(inx)
l = l+1;
end
x1 = x(c1);
figure;stem(x,y,'MarkerFaceColor','red')
figure;stem(x1,h,'MarkerFaceColor','red')