change the dimension of multidimensional matrix

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ABDUL 2018-2-15

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评论： Jan 2018-2-15

hi.... can any one help me in debugging the code . i want to fix the number of rows and number of column to be of variable size or i want to fix number of columns and variable number of rows . in one execution one will be of fixed length and other parameter will be of variable length i have the sample code for your kind reference.

N=64; 
C=16; 
Nt=2;
p=[1 -1 1j -1j];
randn('state', 12345);
B=randsrc(C,N,p); 
for ii=1:Nt
    for n=1:size(B,1)
        B1(n,:,:)=B;
    end
end

B is of size 16 x 64 and after executing B1 i am getting it as 100 x 192 x 2 . i want to retain the size of columns to be 100 x 64 x2 . i want a help on this code.

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Answer 1

Jan 2018-2-15

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I do not understand the question. You have a 16 x 64 matrix and want to get a 100 x 64 x 2 matrix. 100 is not a multiple of 16, so I do not have an idea of what you want exactly. But in general this is done by these commands: repmat, reshape, permute. Any kind of reordering or changing the shape or size of an array can be done using these commands.

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ABDUL 2018-2-15

this is my code i am getting the error message as Error using .* Matrix dimensions must agree. Error in selected_mapping_mimo (line 58) p=[p; B_1(k,:).*ofdm_symbol(:,:,:)]; ofdm_symbol=randn(100,64,2)+(1j*randn(100,64,2));

N=64; C=16; Nt=2; p=[1 -1 1j -1j]; randn('state', 12345); B=randsrc(C,N,p); for ii=1:Nt for n=1:size(B,1) B1(n,:,:)=B; end end p=[]; for k=1:C p=[p; b1(k,:).*ofdm_symbol(:,:,:)]; end

can any one help me in this code to debug it

Jan 2018-2-15

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@ABDUL: Please read http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup . If you format your code, it will be readable.

I do not understand what "retain the code as 16 x 64 x 2 as matrix dimension" means. Maybe you want:

x = rand(16, 64);
y = repmat(x, 1, 1, 2);  % [16 x 64 x 2]

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Answer 2

Jos (10584) 2018-2-15

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Maybe you're looking fo cell arrays, in which each cell can hold a vector of different lengths?

As an example:

Nrows = 10 ; % fixes
Ncolumns = randi(10,Nrows,1) ; % random lengths for each row
B = arrayfun(@(k) randi(10,1,k) , Ncolumns, 'un', 0)
% B{k} is a vector with Ncolumns(k) elements