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.

Question

Biswarup Dutta 2017-3-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/330382-i-am-trying-to-find-the-max-peak-of-the-graph-image-below-without-using-findpeaks-syntax-please

评论： Image Analyst 2017-3-18

采纳的回答： Greg Dionne

robin roy.mat

在 MATLAB Online 中打开

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);

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Answer 1

Greg Dionne 2017-3-17

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https://ww2.mathworks.cn/matlabcentral/answers/330382-i-am-trying-to-find-the-max-peak-of-the-graph-image-below-without-using-findpeaks-syntax-please#answer_259180

[maxval, maxindex] = max(x)

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Biswarup Dutta 2017-3-18

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 2017-3-18

在 MATLAB Online 中打开

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));