How can get all the maximum and minimous values of peaks and valleys in a vector?

In the following code I'm trying to get the maximus and minimous of the graphic; I don't want to use max(i) because that would give me only the higher maximum point and I want the values of every peak and valley The code is shown next:

%close everything and clear everything
close all;
clear all;
clc;
% First we read an image wich must contain a graphic in it and then convert it to black and white
A=im2bw(imread('prueba3.png'));
%Show the image
figure();
imshow(A);
%Obtain the rows and columns
[F,U]=size(A);
i=1;
%Then we "sweep" the matrix looking for the black pixels defined by a 0 and save the
%position "(m,n)" in the vector "x" and "y"
for n=1:U;
     for m=1:F;
         if A(m,n)~=1;
             x(i)=n;
             y(i)=m;
           else
               m=m+1;
           end
       end
       n=n+1;  
       i=i+1;
  end

figure();
plot(x,y);
set(gca, 'YDir', 'reverse')

How can I get the positions of maximus and minimous?

I'm using this image

Thank you very much for your suport

Answer 1

[Yuvaraj Venkataswamy]

Please check the FAQ link.

https://in.mathworks.com/matlabcentral/answers/213619-i-want-to-mark-the-highest-point-of-any-non-black-pixel-within-the-image-to-find-the-max-point

https://in.mathworks.com/matlabcentral/answers/213198-i-want-to-mark-only-the-highest-middle-point-of-binary-image-but-it-show-the-min-point-too