MATLAB: Select graph section using ginput

ginputplot

I would like to find the maximum and minimum on a graph for a section of time defined by ginput. I would also like to save this max min y-value in the variables peak_max and peak_min.
I am having trouble writing this correctly in loop form. This is what I have:
 for i=(1:8)
         y=P(:,i);
         plot(time,y)
         [x,y]=ginput(2);
         pt1=x(1);
         pt2=x(2);
         peak_max(i)=max(y(pt1:pt2)); 
         peak_min(i)=min(y(pt1:pt2));
  end
Basically I want to find the max and min's of each column of data for a specific range and store it. Warnings occur with the storage part.
Any help is appreciated. Thanks.

Best Answer

It looks like you're reassigning y in your code when you call ginput. y should be the ith column of P, but it gets overwritten as the y-coordinate of your click.
Does changing the variable name work? Or, better yet, since you're never using the y value that you click, just discard it:
 for i=(1:8)
    y=P(:,i);
    plot(time,y)
    [x,~]=ginput(2);
    pt1=x(1);
    pt2=x(2);
    peak_max(i)=max(y(pt1:pt2)); 
    peak_min(i)=min(y(pt1:pt2));
 end
Related Question