MATLAB: How to repeat number of array by values in another matrix

repeat

Hello everybody I have an array like array=[3 4 2 1] and I want to create another array which contain repetition of values in this array by no of values in matrix. Matrix =[0 2 4 5; 1 3 2 6; 1 0 3 5; 5 6 3 1] Here for this array first no is 3 this mean repetition in matrix found in first column and row 3 which equal 1 and the second number is 4 also means that second column and forth row. so the resulted array will be 3 4 4 4 4 4 4 2 2 1 1 1 1 1 if someone could help me

Best Answer

array = [3 4 2 1];
matrix = [0 2 4 5; 1 3 2 6; 1 0 3 5; 5 6 3 1];
% first, you need a vector with the same length of array that tells you
% how often each element must be repeated
reps = diag(matrix(array, :));
% now you can use 'repelem' with that vector
result = repelem(array, reps);

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MATLAB: How to rearrange an array ? (only unique numbers in a column)

A = [1 1;1 4;2 3;2 7;3 5;4 2;5 6] ,
c=accumarray(A(:,1),A(:,2),[],@(x) {x})
n=max(cellfun(@numel,c));
B=[unique(A(:,1),'stable') cell2mat(cellfun(@(x) [x' zeros(1,n-numel(x)) ],c,'un',0))]

MATLAB: How can one “summarize a matrix with the first four columns”

Here is one way to do it. There might be some clever way to fully vectorize (eliminate the loop) this, but this will work if performance on huge arrays isn't an issue

% define your original matrix 
A = [1 2 3 4 1.1;1 2 3 4 3; 1 2 3 5 4; 2 3 4 1 6]
% find rows with unique first four elements
 [C,~,ic] = unique(A(:,1:4),'rows')
 
 % summarize by finding average of elements in fifth column over rows with
 % same first four columns
 
 for k = 1:length(ia)
     % use logical indexing to find rows with unique first four elements
     C(k,5) = mean(A(ic==k,5))
 end

Best Answer

Related Solutions

MATLAB: How to rearrange an array ? (only unique numbers in a column)

MATLAB: How can one “summarize a matrix with the first four columns”

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