How to rank 3d matrix across 2 dimensions

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James Spalding on 7 Nov 2022
Answered: Bruno Luong on 7 Nov 2022
Hi Everyone,
I have 5 variables of gridded data that are identical in size (361x181 matrices). I have run these through different scenerios for my anaylsis and now am trying to compare the changes. What I would like to do is create a 3-d matrix of all the variables sorted by highest to lowest (361x181x5) but retain the "name" of the vairable so I can say this variable had the most change at this location.
From what I have been able to find online the best way seems to be to create a cell of off the variables and then sort.
The issue i am having is sorting the cell along the correct dimesions with the associated names. See the code I've tried so far below, the variables are attached
iVars = zeros(361,181,5);
iVars(:,:,1) = var1;
iVars(:,:,2) = var2;
iVars(:,:,3) = var3;
iVars(:,:,4) = var4;
iVars(:,:,5) = var5;
iNames = {'Var 1','Var 2','Var 3','Var 4','Var 5'};
[~,VarSORT]=sort(iVars,3,'descend');
iNames(VarSORT);
Any help or suggestions is greatly appreciated!
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James Spalding on 7 Nov 2022
Hi all,
So i have found a "forced" solution for this problem that takes a while but does work (see code below)
If anyone can come up with a better solution that doesn't run the risk of my computer suddenly bursting into flames let me know I'd appreciate it!
James
%rank vars in single variable
iVars = zeros(361,181,5);
iVars(:,:,1) = var1;
iVars(:,:,2) = var2;
iVars(:,:,3) = var3;
iVars(:,:,4) = var4;
iVars(:,:,5) = var5;
VarsRank=cell(361,181);
for j = 1:361
for k = 1:181
val1=table(iVars(j,k,1),"Var1");
val2=table(iVars(j,k,2),"Var2");
val3=table(iVars(j,k,3),"Var3");
val4=table(iVars(j,k,4),"Var4");
val5=table(iVars(j,k,5),"Var5");
irnk=[val1;val2;val3;val4;val5];
RNK=sortrows(irnk,1,'descend');
VarsRank{j,k}=irnk;
fprintf("on iteration\n")
t=j*k;
disp(t)
fprintf('of 65341')
end
end

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Answers (2)

Matt J on 7 Nov 2022
Is this (simplified) not what you want?
iVars=rand(3,3,5);
iNames = {'Var 1','Var 2','Var 3','Var 4','Var 5'};
[~,VarSORT]=sort(iVars,3,'descend');
iNames=iNames(VarSORT)
iNames = 3×3×5 cell array
iNames(:,:,1) = {'Var 5'} {'Var 4'} {'Var 1'} {'Var 2'} {'Var 1'} {'Var 1'} {'Var 4'} {'Var 3'} {'Var 3'} iNames(:,:,2) = {'Var 2'} {'Var 1'} {'Var 4'} {'Var 5'} {'Var 3'} {'Var 4'} {'Var 2'} {'Var 5'} {'Var 5'} iNames(:,:,3) = {'Var 1'} {'Var 3'} {'Var 5'} {'Var 3'} {'Var 2'} {'Var 2'} {'Var 5'} {'Var 1'} {'Var 1'} iNames(:,:,4) = {'Var 4'} {'Var 5'} {'Var 3'} {'Var 1'} {'Var 5'} {'Var 5'} {'Var 3'} {'Var 4'} {'Var 2'} iNames(:,:,5) = {'Var 3'} {'Var 2'} {'Var 2'} {'Var 4'} {'Var 4'} {'Var 3'} {'Var 1'} {'Var 2'} {'Var 4'}
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Bruno Luong on 7 Nov 2022
iNames(VarSORT);
won't change iNames, you need to assign the expression to a variable VarsRank
iVars = zeros(361,181,5);
iVars(:,:,1) = var1;
iVars(:,:,2) = var2;
iVars(:,:,3) = var3;
iVars(:,:,4) = var4;
iVars(:,:,5) = var5;
iNames = {'Var 1','Var 2','Var 3','Var 4','Var 5'};
[~,VarSORT]=sort(iVars,3,'descend');
VarsRank = iNames(VarSORT); % Assign the result to a variable
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