MATLAB: Index and matrix selection

selecting data from matrix

Hi,

my index matrixis size(index)=118*4. the data matrix is size(data)=2970290*9

iwa nt to select just index-data.

i wrote this:

data_new=data([index],:). the size of this matrix is:472*9.

I want to get the matrix with the size 118*36. I dont want to use reshape. do you know something better than my statement (data_new=data([index],:))

Thanks

Best Answer

 cell2mat(arrayfun(@(x) {data(x,:)},index,'uniformoutput',false));

Using reshape should be faster though.

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MATLAB: Creating a vector from a(:) : b(:) , but one for each index without using loops.

a=[1,2,3];
b=[6,4,9];
result = cell2mat(arrayfun(@(x,y)x:y,a,b,'un',0));

ADD

a = randi(150,32,4,4,4); % your 4-D array
idx = {1:32,3,2,1};      % your array with indexs
[i1,i2,i3,i4] = ndgrid(idx{:});
i1 = cell(1,4);
[i1{:}] = ndgrid(idx{:});
result = a(sub2ind(size(a),i1{:}));

MATLAB: 2D indexing of 3D array

% Your input data
A=rand(20,5);
index=[1 2 3; 10 11 12; 15 16 17]';
% Get the dimensions, for convenience and clarity
a2 = size(A,2);
[i1 i2] = size(index);
% Calculate the output
output = reshape(A(index,1:a2),[i1 i2 a2])

Best Answer

Related Solutions

MATLAB: Creating a vector from a(:) : b(:) , but one for each index without using loops.

MATLAB: 2D indexing of 3D array

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