Why does this technique not work?

I have a mat file which has a row vector u and a matrix temp_gbo. The size of this matrix is 100 x 4. I want the following:

Each row of the matrix temp_gbo must have the same arrangment of elements as is in u.The mat file and the script "swapping" are attached but the script doesn't fulfill my requirement. How should I modify this code?

clear;clc

load 2F_and_1J_Noise0
temp_gbo

temp_gbo = 100x4

88.4028 38.5065 46.0277 4.7098 38.5561 64.7773 75.2408 3.0414 60.7072 31.7335 84.1475 0.4325 51.2496 179.9745 75.4241 1.9322 36.0663 91.9651 5.9596 2.4260 27.8965 61.4317 81.2432 4.9581 54.8198 33.0297 38.9350 0.4600 51.3407 38.9219 74.6855 0.4327 155.7973 48.8800 66.5703 3.9794 37.2537 86.8754 9.0043 4.3471

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u

u = 1x4

33.0000 60.0000 80.0000 1.2000

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% Create an index mapping based on the ordering in u
[~, idx] = sort(u)

idx = 1x4

4 1 2 3

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% Rearrange each row of temp_gbo to match the order in u
sorted_temp_gbo = arrayfun(@(i) temp_gbo(i, idx), 1:size(temp_gbo, 1), 'UniformOutput', false);
% Convert cell array back to matrix
sorted_temp_gbo = cell2mat(sorted_temp_gbo');

% Display results
disp('Rearranged temp_gbo:');

Rearranged temp_gbo:

disp(sorted_temp_gbo);

    4.7098   88.4028   38.5065   46.0277
    3.0414   38.5561   64.7773   75.2408
    0.4325   60.7072   31.7335   84.1475
    1.9322   51.2496  179.9745   75.4241
    2.4260   36.0663   91.9651    5.9596
    4.9581   27.8965   61.4317   81.2432
    0.4600   54.8198   33.0297   38.9350
    0.4327   51.3407   38.9219   74.6855
    3.9794  155.7973   48.8800   66.5703
    4.3471   37.2537   86.8754    9.0043
    4.3438   52.9683   20.9183   82.5033
    4.7273   47.6448   15.3711   82.2237
    0.9042   65.0012   27.4686   91.4664
    4.6909   88.4891   31.2764   30.2764
    1.0624   27.0809   58.7502   75.6295
    4.2156   37.1013   89.1705    3.1686
    4.0597   40.8265   85.0226   22.6161
    2.6292   37.4192   64.3769   77.7092
    2.4569   35.6162   68.1268   91.9500
    3.3988   52.6940         0   79.5701
    0.5169   24.7223   55.8234   72.4056
    3.4761   85.5143   34.7750         0
    1.9327   86.0476   39.6672    0.4948
    4.7357   88.4182   34.5185    0.6006
    2.0391  180.0000   50.1649   71.7617
    4.5950   47.1916   91.6507   52.6494
    4.0385   37.5877   85.3056         0
    1.0422   57.8052   14.3757   73.2256
    0.6285   31.9638   57.4676   47.1311
    3.9067   31.8537   54.3263   54.9414
    4.5741   41.7440   82.6068         0
    5.0000   47.3462  180.0000   70.1522
    4.2515   43.4673   84.9375   37.3158
    0.7602   51.9906   28.7342   68.7879
    2.2839   52.4258   29.8845   69.4983
    4.0376   29.2728   61.5666   88.4511
    2.8283   20.2754   56.0599   76.2128
    3.9744   39.8841   86.5460   26.7284
    2.3869   62.1685   36.2030   81.6113
    1.8585   33.5541   59.2858   63.9540
    4.2237   87.3762   37.1852    3.3405
    4.9551   41.4211   49.4507   57.2578
    2.7559   25.6862   48.5205   74.2897
    3.7116   48.8804   33.2311   62.7674
    0.9317   62.7828   36.0722   81.3585
    1.2161   49.9005   65.6788   78.4954
    1.4451   31.7006   55.3651   68.5411
    3.6662   87.4762   36.8995         0
    1.0496   93.8907   43.6019   13.1058
    0.3931   53.0157  180.0000   61.1421
    1.5544   34.4059   82.6804         0
    5.0000   52.3391   16.2593   77.4597
    0.9870   54.5280   33.4112   74.8179
    3.2812   42.9704   86.6939   34.2715
    1.3005   34.0263   62.9864   87.8448
    3.9304  172.4801   54.4332   73.9627
    0.3111   51.1589    8.6070   64.4341
    2.4900   33.2038   90.9118         0
    2.1520   37.0995   63.6866   84.1506
    3.5267   87.2596   35.8582    4.7209
    1.1037   85.0783   43.5476    8.4147
    0.4104   46.3361  173.1743    0.7823
    0.1996   71.1619   47.0687   95.7982
    1.4369   92.2919   44.2698   17.8745
    0.8587  180.0000   52.4932   70.1372
    0.4115   57.2047   32.8462   64.8573
    1.6112   33.0698   55.7516   71.6088
    3.5221   51.8262    1.1651   70.1198
    1.1918   47.5856   70.4000   86.2674
    0.8800   70.2843   44.9222   94.0877
    1.4681   93.8373   37.9288   39.5883
    3.0089   85.4664   36.5468    0.2763
    3.3264   89.7302   41.4511   37.6632
    0.6193   50.7589  178.4640   42.7516
    0.9991   56.8364   23.8414   65.1099
    1.7919   53.3839   30.5285   81.9275
    1.4039   60.3241   33.6689   73.5722
    1.6628   56.9396   33.5052   74.8300
    4.5622   35.9324   89.3568   51.3955
    5.0000   49.7089  173.6502   82.2179
    2.1364   68.1138   45.6288   80.4482
    2.5751   86.8272   42.0998   23.0540
    1.8130   40.4551   56.2903   66.2560
    2.2854   50.5136   17.1055   71.8211
    1.9451   40.4900   89.2407    3.8861
    2.0499   19.2196   52.4555   72.9366
    0.9984   25.8133   55.8932   72.7862
    0.3682         0   54.5734   31.5113
    3.2901   58.5582   33.0217   83.1362
    0.6797   44.7811         0   39.2843
    3.5797   54.9605   12.3977   81.3156
    4.1099   40.6917   88.0154   25.5098
    1.6345   87.2932   38.6123   14.3557
    1.7437   53.3069   35.8710   71.3681
    0.6821   51.2858  169.4714   69.2238
    3.1260   37.3071   90.4495    2.1839
    0.6866   56.7592   19.5314   83.4022
    0.7968   97.2518   39.5505   38.2560
    3.7702    5.6820   50.1955   72.5416
    1.5873   48.2611   34.8206   48.1632

Answer 1

[Torsten]

I already gave you the code how to order a vector according to the ordering of "u". Why don't you use it ?

Your method is wrong. You get the order of the elements of u from the command

[~, idx] = sort(u)

as

[4 1 2 3]

Now if you order the elements of temp_gbo according to temp_gbo(i,idx), you put the element in column 4 in column 1, the element of column 1 in column 2, the element of column 2 in column 3 and the element of column 3 in column 4. But why should this reflect the ordering of u ? You don't use the ordering of the ith row of temp_gbo in any way.

[Sadiq Akbar]

@Torsten

Thanks a lot for your kind response. Yes, you are right. But now I want to try this new one. But how to modify this new code so that it meets my requirement?

[Torsten]

load 2F_and_1J_Noise0;
u 

u = 1x4

33.0000 60.0000 80.0000 1.2000

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temp_gbo

temp_gbo = 100x4

88.4028 38.5065 46.0277 4.7098 38.5561 64.7773 75.2408 3.0414 60.7072 31.7335 84.1475 0.4325 51.2496 179.9745 75.4241 1.9322 36.0663 91.9651 5.9596 2.4260 27.8965 61.4317 81.2432 4.9581 54.8198 33.0297 38.9350 0.4600 51.3407 38.9219 74.6855 0.4327 155.7973 48.8800 66.5703 3.9794 37.2537 86.8754 9.0043 4.3471

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[~, iu] = sort(u); 
sorted_temp_gbo = zeros(size(temp_gbo));
for i = 1:size(temp_gbo, 1)        
    [~,itemp(iu)] = sort(temp_gbo(i,:));
    sorted_temp_gbo(i,:) = temp_gbo(i,itemp);        
end
sorted_temp_gbo

sorted_temp_gbo = 100x4

38.5065 46.0277 88.4028 4.7098 38.5561 64.7773 75.2408 3.0414 31.7335 60.7072 84.1475 0.4325 51.2496 75.4241 179.9745 1.9322 5.9596 36.0663 91.9651 2.4260 27.8965 61.4317 81.2432 4.9581 33.0297 38.9350 54.8198 0.4600 38.9219 51.3407 74.6855 0.4327 48.8800 66.5703 155.7973 3.9794 9.0043 37.2537 86.8754 4.3471

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[Sadiq Akbar]

@Torsten

Thanks a lot for your kind response. Yes, it works but I am asking what's the problem with my new code? Further, how can we modify it so that it does the same thing as you have done now.

[Torsten]

Yes, it works but I am asking what's the problem with my new code?

Cited from my previous answer:

Your method is wrong. You get the order of the elements of u from the command

[~, idx] = sort(u)

as

[4 1 2 3]

Now if you order the elements of temp_gbo according to temp_gbo(:,idx), you put the elements in column 4 in column 1, the elements of column 1 in column 2, the elements of column 2 in column 3 and the elements of column 3 in column 4. But why should this reflect the ordering of u ? You don't use the ordering of the ith row of temp_gbo in any way.

Further, how can we modify it so that it does the same thing as you have done now.

I'd say that the corrected version of your code is near to your original. So I already did the modification you are asking for. I doubt you can use "arrayfun" in the correct version because you have to execute two commands in the loop. And "arrayfun" looks short and fast, but it's usually slower than a simple loop.

[Sadiq Akbar]

@Torsten

Thanks a lot for your kind response. Yes, you are saying correctly.

I doubt you can use "arrayfun" in the correct version because you have to execute two commands in the loop: So can you modify my "arrafun" so that it does the same as does yours.

[Torsten]

So can you modify my "arrafun" so that it does the same as does yours.

I don't use "arrayfun", I use a loop. And I don't think that "arrayfun" is applicable in this corrected version of your code for the reason already mentionned.

load 2F_and_1J_Noise0;
u 

u = 1x4

33.0000 60.0000 80.0000 1.2000

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temp_gbo

temp_gbo = 100x4

88.4028 38.5065 46.0277 4.7098 38.5561 64.7773 75.2408 3.0414 60.7072 31.7335 84.1475 0.4325 51.2496 179.9745 75.4241 1.9322 36.0663 91.9651 5.9596 2.4260 27.8965 61.4317 81.2432 4.9581 54.8198 33.0297 38.9350 0.4600 51.3407 38.9219 74.6855 0.4327 155.7973 48.8800 66.5703 3.9794 37.2537 86.8754 9.0043 4.3471

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[~, iu] = sort(u); 
sorted_temp_gbo = zeros(size(temp_gbo));
for i = 1:size(temp_gbo, 1)        
    [~,itemp(iu)] = sort(temp_gbo(i,:));
    sorted_temp_gbo(i,:) = temp_gbo(i,itemp);        
end
sorted_temp_gbo

sorted_temp_gbo = 100x4

38.5065 46.0277 88.4028 4.7098 38.5561 64.7773 75.2408 3.0414 31.7335 60.7072 84.1475 0.4325 51.2496 75.4241 179.9745 1.9322 5.9596 36.0663 91.9651 2.4260 27.8965 61.4317 81.2432 4.9581 33.0297 38.9350 54.8198 0.4600 38.9219 51.3407 74.6855 0.4327 48.8800 66.5703 155.7973 3.9794 9.0043 37.2537 86.8754 4.3471

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Answer 2

[Abhas]

Hi Sadiq,

To achieve the specified order based on the relative magnitudes within each row of "temp_gbo", you need to sort each row and then rearrange the elements according to the specified positions.

Here's the MATLAB code to perform the required steps:

clear; clc;

load 2F_and_1J_Noise0;

% Define the new order based on the relative magnitudes
new_order = [2, 3, 4, 1]; % 2nd lowest, 3rd lowest, 4th lowest, lowest

% Preallocate the sorted matrix
sorted_temp_gbo = zeros(size(temp_gbo));

% Rearrange each row of temp_gbo to match the specified order
for i = 1:size(temp_gbo, 1)
    [~, sort_idx] = sort(temp_gbo(i, :)); % Get the indices of the sorted elements
    sorted_temp_gbo(i, :) = temp_gbo(i, sort_idx(new_order)); % Rearrange according to new_order
end

% Display results
disp('Rearranged temp_gbo:');
disp(sorted_temp_gbo);

Output:

You may refer to the following MathWorks documentation link to have a better understanding on array indexing: https://www.mathworks.com/help/matlab/math/matrix-indexing.html

[Sadiq Akbar]

@Abhas

Thanks a lot for your kind response. How did you write the new order:

new_order = [2, 3, 4, 1]; % 2nd lowest, 3rd lowest, 4th lowest, lowest

2ndly what is the problem with my code?

[Abhas]

Hey @Sadiq Akbar!

The new_order is based on the ordering of elements in u. You can have a look on the ordering of elements in your code, which is causing the problem.

[Sadiq Akbar]

@Abhas

Thanks a lot for your kind response.

1-How did you decide the ordering of elements of u? I am not getting you.

2-What is the problem with my code. I want to use my code but how should I modify it to meet my requirement?

[Abhas]

1. Determine the new positions of each element in u after sorting, and use this order to rearrange the elements in each row of temp_gbo.
2. The command you used only provides the order of the elements in u, but it does not specify how to rearrange the elements in temp_gbo accordingly. In my code it specifies the order in which the smallest, second smallest, third smallest and largest element should be placed at.

Answer 3

[Steven Lord]

Setup

Let's generate a collection of possible rows.

u = randi(10, 6, 3);

Let's ensure that no row in u has the exact same values as another row, though perhaps in a different order.

s = sort(u, 2);
while height(unique(s, 'rows')) < height(u)
    u = randi(10, 6, 3);
    s = sort(u, 2);
end
u

u = 6x3

7 10 6 10 3 7 4 10 10 8 1 9 1 2 3 10 7 8

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Now create the matrix and reorder each row in A arbitrarily.

whichrow = randi(height(u), 8, 1);
A = u(whichrow, :);
for therow = 1:height(A)
    A(therow, :) = A(therow, randperm(width(A)));
end
A

A = 8x3

3 7 10 7 10 6 10 3 7 10 4 10 8 10 7 10 7 6 10 7 6 4 10 10

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The algorithm

We can use ismember (or you may want to use ismembertol if your data is not integer valued) to determine which row in u was used to generate each shuffled row in A. First we sort the rows in u and A then we ask whether each row in Asorted is present in s (we know that it is, so I can ignore that output) and which row of s the corresponding row of Asorted is.

s = sort(u, 2);
Asorted = sort(A, 2);
[~, ind] = ismember(Asorted, s, 'rows');

Trust but verify

To check, does this match the contents of whichrow, which is the variable we used to construct A in the first place?

[ind, whichrow]

ans = 8x2

2 2 1 1 2 2 3 3 6 6 1 1 1 1 3 3

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Looks good to me.

[Sadiq Akbar]

@Steven Lord

Thanks a lot for your kind response. I thought too much about your code but I am not getting you what have you tried to make me understand. I am sorry for that.

[Torsten]

@Steven Lord

Since i remember the previous question @Sadiq Akbar asked, his aim is to find code for the following problem:

Given two vectors u and v of length n, find the ordered vector v_ordered of length n such that if u(i) is the j-th biggest element of u, then v_ordered(i) is the j-th biggest element of v for 1 <= i <= n.