Printing row of maximum value of a column

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ennes mulla 2021-7-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/874853-printing-row-of-maximum-value-of-a-column

回答： Shlok 2024-8-30，5:38

Hi.

I am processing image data for an experiment I have where i try to track the centroid of laser beam on a detector.

I was able to extract the data and process them to find the areas of all shapes in the image and to find all their centroid. The centroid has two coordinates X and Y. I have created an array that has 3 columns, where the columns are area of each shape and the coordinate of its centeroidm as following: 'Area', 'X','Y'. I have used the following code:

directory = 'C:\Users\anask\Desktop\test\';
files = dir([directory '/*.jpg']);
[~,index] = sortrows({files.date}.'); files = files(index); clear index;
auxx = [];
auxy = [];
for x = 1: numel(files)
    A= imread([directory '/' files(x).name]);
%Convert the image ino binary image
    Ibw = im2bw(A);
%Fill image regions and holes
    Ibw = imfill(Ibw,'holes');
    Ilabel = bwlabel(Ibw);
%find the centroid
    stat = regionprops(Ibw,'Area','Centroid'); %Note here stat is a struct array
end    

Till here I have the stat array that has Area and Centroid coorinate but for all images and I want it to apply the following processing to every image

%Creating new array that have Area, X-coordinate, Y-coordinate
    area = cat(1,stat.Area)
    Coor = cat(1,stat.Centroid)
%Combaining the results in one Array
    Array = cat(2,area,Coor)
%Adding a header to the array    
    header = {'Area','x','y'};
    Array = [header; num2cell(Array)];
  

Then I want to append in a new matrix or Array that has the whole row of max 'Area' from every image.

Can someone help me please?

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Answer 1

Shlok 2024-8-30，5:38

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Hi Ennes,

To extract the maximum area value from each image and store it in a new array, you should preprocess this data inside the for loop when accessing each image file. Within this loop, you'll extract and append the row corresponding to the maximum "Area" value, then store it in an array. Here's how you can achieve this:

directory = 'C:\Users\anask\Desktop\test\'; 
files = dir([directory '/*.jpg']); 
[~, index] = sortrows({files.date}.');  
files = files(index);  
clear index; 
  
% Initialize an empty array to store the rows with maximum area 
maxAreaArray = []; 
  
for x = 1:numel(files) 
    A = imread([directory '/' files(x).name]); 
    Ibw = im2bw(A); 
    Ibw = imfill(Ibw, 'holes'); 
    Ilabel = bwlabel(Ibw); 
     
    stat = regionprops(Ibw, 'Area', 'Centroid');  
 
    % Extract the values from ‘stat’ object 
    area = cat(1, stat.Area); 
    Coor = cat(1, stat.Centroid); 
    Array = cat(2, area, Coor); 
     
    % Find the row with the maximum area 
    [~, maxIdx] = max(area); 
    maxRow = Array(maxIdx, :); 
     
    % Append the row with the maximum area to the maxAreaArray 
    maxAreaArray = [maxAreaArray; maxRow]; 
end 
header = {'Area', 'x', 'y'}; 
maxAreaArray = [header; num2cell(maxAreaArray)]; 

This will provide you with an array where each row corresponds to the largest shape detected in each image, including its area and centroid coordinates.