MATLAB: Find groups of duplicate values and preserving order

MATLABmatrix manipulation

Hi all,
I have a 100×1 double matrix 
matrix=[100--100].*rand(100,1)-100;
C=unique(matrix);
I would love to create a length(C) x length(matrix) matrix which contains the positioning index from matrix to later conduct a function.
Thank you for your time,

Best Answer

The code below is far from optimal, but it should help you out. It assumes there is always an L to load, and you have enough memory to store all the different mat files in a library. These assumptions are to memoization. You could improve the readability of this code by creating a masterlist of indices and file names, instead of endless elseifs. Then it is very easy to add or remove a new mat and it makes your code more readable. You can also check if the output of ismember sums to 1 to check for valid inputs.
function L=load_mat(Bi)
persistent L_libary
if isempty(L_libary),L_libary={};end
if numel(L_libary)>=Bi && ~isempty(L_libary{Bi})
    L=L_libary{Bi};
end
if Bi==11
    L = load('110.mat');
elseif Bi==12
    L = load('120.mat');
elseif Bi==13
    L = load('130.mat');
elseif Bi==14
    L = load('140.mat');
elseif Bi==15
    L = load('150.mat');
elseif Bi==16
    L = load('160.mat');
elseif Bi==17
    L = load('170.mat');
elseif Bi==18
    L = load('180.mat');
elseif Bi==19
    L = load('190.mat');
elseif Bi==191
    L = load('191.mat');
elseif Bi==192
    L = load('192.mat');
elseif Bi==193
    L = load('193.mat');
elseif Bi==21
    L = load('210.mat');
elseif Bi==22
    L = load('220.mat');
elseif Bi==23
    L = load('230.mat');
elseif Bi==24
    L = load('240.mat');
elseif Bi==25
    L = load('250.mat');
elseif Bi==26
    L = load('260.mat');
elseif Bi==27
    L = load('270.mat');
elseif Bi==28
    L = load('280.mat');
elseif Bi==29
    L = load('290.mat');
elseif Bi==291
    L = load('291.mat');
elseif Bi==292
    L = load('292.mat');
elseif Bi==293
    L = load('293.mat');
elseif Bi==31
    L = load('310.mat');
elseif Bi==32
    L = load('320.mat');
elseif Bi==33
    L = load('330.mat');
elseif Bi==34
    L = load('340.mat');
elseif Bi==35
    L = load('350.mat');
elseif Bi==36
    L = load('360.mat');
elseif Bi==37
    L = load('370.mat');
elseif Bi==38
    L = load('380.mat');
elseif Bi==39
    L = load('390.mat');
elseif Bi==391
    L = load('391.mat');
elseif Bi==392
    L = load('392.mat');
elseif Bi==393
    L = load('393.mat');
end
L_libary{Bi}=L;
end
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