Find maximum for each Image in table

Good evening,

I have a similar issue like my previous question (For Loop Table Matlab - MATLAB Answers - MATLAB Central (mathworks.com)).

I have a small excerpt of my table. In the coloumn Label you see my Images and in the column MaxPosition and Intenisty my measurements.

Number              Label               MaxPosition        Intensity
    ______    __________________________    ___________    ________
       1      {'Image0100 16-28-31.bmp'}         94            10   
       2      {'Image0100 16-28-31.bmp'}        123            8   
       3      {'Image0101 16-28-46.bmp'}         95            23   
       4      {'Image0101 16-28-46.bmp'}        124            43   
       5      {'Image0102 16-29-01.bmp'}         95            22   
       6      {'Image0102 16-29-01.bmp'}        125            54   
       7      {'Image0103 16-29-16.bmp'}         96            94   
       8      {'Image0103 16-29-16.bmp'}        126            30   
       9      {'Image0104 16-29-31.bmp'}         98            49   
      10      {'Image0104 16-29-31.bmp'}        127            39   
      11      {'Image0105 16-29-46.bmp'}         98            20   
      12      {'Image0105 16-29-46.bmp'}        128            10   
      13      {'Image0106 16-30-01.bmp'}         98            2   
      14      {'Image0106 16-30-01.bmp'}        128            94   
      15      {'Image0107 16-30-16.bmp'}         99            93   
      16      {'Image0107 16-30-16.bmp'}        129            54   
      17      {'Image0108 16-30-31.bmp'}        100            32   
      18      {'Image0108 16-30-31.bmp'}        130            44

Now I want to find the max of the Intensity for every Image with the corresponding MaxPosition.

I use varfun but this command gives me the max of the MaxPosition and the max of the Intensity of every Image, not the corresponding one.

For example for Image0100 the max Intensity is 10 and the correpsonding to it is 94. And I want to display 94 in my new table.

Thanks.

Best

Pouyan

[Walter Roberson]

findgroups() splitapply()

[Pouyan Sadeghian]

Hey @Walter Roberson,

thank you for your response. I tried to understand these commands and tried to use them but I think it does not solve my problem.

Maybe my question is not clear.

l have for every image multiple measurements for Intensity and for MaxPosition. What I need is the maximum value of the Intensity for each image with the corresponding MaxPosition value to the Intensity.

I think what I get with your commands is the maximum value of Intensity and the maximum value of MaxPosition for each image. But I do not need this.

Or maybe I use these commanda false.

I hope you could understand my question better.

Best

Answer 1

[Duncan Po]

You can use groupsummary to find the maximum value of each group:

T1 = groupsummary(T, 'MaxPosition', 'max', 'Intensity');

[Walter Roberson]

Even better!

[Pouyan Sadeghian]

Thanks @Duncan Po for your response.

Its a very easy and quick command.

I was searching about a command like this. I used varfun but it did not solve my problem.

Best

Pouyan

Answer 2

[Walter Roberson]

 data = {
       1      {'Image0100 16-28-31.bmp'}         94            10   
       2      {'Image0100 16-28-31.bmp'}        123            8   
       3      {'Image0101 16-28-46.bmp'}         95            23   
       4      {'Image0101 16-28-46.bmp'}        124            43   
       5      {'Image0102 16-29-01.bmp'}         95            22   
       6      {'Image0102 16-29-01.bmp'}        125            54   
       7      {'Image0103 16-29-16.bmp'}         96            94   
       8      {'Image0103 16-29-16.bmp'}        126            30   
       9      {'Image0104 16-29-31.bmp'}         98            49   
      10      {'Image0104 16-29-31.bmp'}        127            39   
      11      {'Image0105 16-29-46.bmp'}         98            20   
      12      {'Image0105 16-29-46.bmp'}        128            10   
      13      {'Image0106 16-30-01.bmp'}         98            2   
      14      {'Image0106 16-30-01.bmp'}        128            94   
      15      {'Image0107 16-30-16.bmp'}         99            93   
      16      {'Image0107 16-30-16.bmp'}        129            54   
      17      {'Image0108 16-30-31.bmp'}        100            32   
      18      {'Image0108 16-30-31.bmp'}        130            44};
 T = cell2table(data, 'VariableNames', {'Number', 'Label', 'MaxPosition', 'Intensity'});
 T(1:5,:)

ans = 5×4 table
    Number              Label               MaxPosition    Intensity
    ______    __________________________    ___________    _________

      1       {'Image0100 16-28-31.bmp'}         94           10    
      2       {'Image0100 16-28-31.bmp'}        123            8    
      3       {'Image0101 16-28-46.bmp'}         95           23    
      4       {'Image0101 16-28-46.bmp'}        124           43    
      5       {'Image0102 16-29-01.bmp'}         95           22    

 
 [G, ID] = findgroups(T.Label);
 results = cell2mat(splitapply(@findmax, T.MaxPosition, T.Intensity, G));
 
 output = table(ID, results(:,1), results(:,2), 'VariableNames', {'Label', 'Intensity', 'MaxPosition'});
 output

output = 9×3 table
              Label               Intensity    MaxPosition
    __________________________    _________    ___________

    {'Image0100 16-28-31.bmp'}       10             94    
    {'Image0101 16-28-46.bmp'}       43            124    
    {'Image0102 16-29-01.bmp'}       54            125    
    {'Image0103 16-29-16.bmp'}       94             96    
    {'Image0104 16-29-31.bmp'}       49             98    
    {'Image0105 16-29-46.bmp'}       20             98    
    {'Image0106 16-30-01.bmp'}       94            128    
    {'Image0107 16-30-16.bmp'}       93             99    
    {'Image0108 16-30-31.bmp'}       44            130    

 
 function results = findmax(Pos, Inten)
    [maxinten, idx] = max(Inten);
    results = {maxinten, Pos(idx)};
 end
 

[Pouyan Sadeghian]

Thank you @Walter Roberson for your step by step response. I tried to understand the steps.

I save directly the table in the workspace.

But I get an error. I searched online but I dont know how to solve that.

Maybe you can help me further.

Thanks.

Best

[Walter Roberson]

You did not save the code for findmax. I posted it above -- it is directly below the results.

[Pouyan Sadeghian]

Right, I forgot it.

Thank you Walter. It works perfect for my project!

Best

Pouyan

[Walter Roberson]

@Duncan Po's response is better than mine for this purpose !

[Pouyan Sadeghian]

Hey @Walter Roberson,

alright.

I used your code and It satifies my problem but youre right. His response is shorter and easier.

Thank you

Answer 3

[Sulaymon Eshkabilov]

A = ... % Table of all data
B = A.MaxPosition;  % Separate out the column

[Pouyan Sadeghian]

Hi @Sulaymon Eshkabilov,

thank you for your response. Maybe you dont understand my problem or I explain it not clearly.

I want to find the max value of the Intensity for each image with the corresponding MaxPosition.

For example the maximum Intensity for image0101 is 43 (line 4) and I want also the corresponding MaxPosition to the maximum Intensity which is 124.

Maybe this is more understandable.