MATLAB: How to interpolate a graph to find a point halfway from the max peak

Question

Hi, I am wondering how to find a point halfway from the maximum point (thats pointing down the way) on the graph I created:

http://www.2shared.com/photo/pIak1Za9/graph1.html

It was made using the code

I = imread('f_000021.tif','TIFF'); imshow('f_000021.tif') x=[128 180]; y=[50 50]; improfile(I,x,y) plot(max)

There isn't many pixels plotted so I was wondering if I could pick a point in between a couple of pixels on that graph (half of the maximum value)?

Thanks, Graham

Answer 1

Do you search for something like this?

V = sin(0:0.01:pi/2);
maxV = max(V);
minV = min(V);
Range = maxV - minV;
HalfIndex = find(V > maxV - Range / 2, 1, 'first');

You have to adjust the signs and > or < according to your exact problem.