I am trying to find the max peak of the graph (image below) without using 'findpeaks' syntax. Please help me out. The .mat file is attached.

I am using the following code to plot the graph:

clc
a=importdata('robin roy.mat');
b=a.data;
x=b(22000:25830,1);
x(x<0)=[];
plot(x);

Answer 1

[Greg Dionne]

[maxval, maxindex] = max(x)

[Biswarup Dutta]

Hi Greg, Thanks for your reply. I can't understand your answer. Can you please mention the complete code?

[Greg Dionne]

That is the complete code.

try "help max" the first output gives you the maximum value. The second output gives you the index of the maximum value.

Good luck.

[Image Analyst]

This will find the max peak location and its value. How many peaks were you expecting?

[Biswarup Dutta]

Hi Greg, Thanks for your help. Now, I get that. But one more thing, the max value I get is 1.22. How can I get the value of the point on X-axis, where the peak exists?

[Image Analyst]

What does that mean? You get BOTH the height of the curve (x=1.22), and the index where it occurs. What more do you want?

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 25;

storedStructure = importdata('robin roy.mat');
b = storedStructure.data;
x = b(22000:25830,1);
x(x<0) = [];
plot(x, 'b-', 'LineWidth', 2);
grid on;
xlabel('Index', 'FontSize', fontSize);
ylabel('x', 'FontSize', fontSize);
[maxXValue, indexOfMaxXValue] = max(x)
% Draw lines to the peak
line([indexOfMaxXValue, indexOfMaxXValue], [0, maxXValue],...
  'LineWidth', 2, 'Color', 'r');
line([1, indexOfMaxXValue], [maxXValue, maxXValue],...
  'LineWidth', 2, 'Color', 'r');
message = sprintf('The max value of %f\noccurs at an index of %d.',...
  maxXValue, indexOfMaxXValue);
uiwait(helpdlg(message));

Answer 2

[Image Analyst]

Try the attached.