How I can split a matrix in four matrixes

Question

Maryam Hamrahi 2016-6-28

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https://ww2.mathworks.cn/matlabcentral/answers/292578-how-i-can-split-a-matrix-in-four-matrixes

回答： David Sanchez 2016-6-28

I have a nx3 matrix and I would like to split it in four matrices with different number of rows and three columns. any help is appreciated.

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Stephen23 2016-6-28

So if the number of rows n is unknown, how many rows are in each of the four matrices ?

Have you tried using indexing, or mat2cell ?

Maryam Hamrahi 2016-6-28

Number of rows in each matrices are not important. I am applying a code whcih contains a loop and it gives me error when the number of rows are more than 10000. So, I want to split the matrix to prevent the error.

I just need split the matrix in smaller matrices.

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Answer 1

KSSV 2016-6-28

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clc; clear all ;
A = rand(100,3) ;   % rows should be greater then 4 
a = size(A,1);      % rows in A
n = 4;              % number of partitions 
out = diff([0,sort(randperm(a-1,n-1)),a]);   % split rows into four random parts 
% else you enter your own four numbers such that sum is size(A,1)
% four matrices
A1 = A(1:out(1),:) ;
A2 = A(out(1)+1:out(1)+out(2),:) ;
A3 = A(out(2)+1:out(2)+out(3),:) ;
A4 = A(out(3)+1:out(3)+out(4),:) ;

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Answer 2

David Sanchez 2016-6-28

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M = rand(1001,3); % your matrix
L = size(M,1); % L = number of rows
n = floor(L/4); % number of rows for your matrices
N = cell(4,1);
for k=1:3
    N{k,1} = M( ((k-1)*n+1):n*k,: );
end
N{4,1} = M((3*n+1):L,:);
% to access your matrices...
N_1  = cell2mat(N(1,1));