change the dimension of multidimensional matrix

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ABDUL
ABDUL 2018-2-15
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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回答（2 个）

Jan
Jan 2018-2-15
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
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
Jan 2018-2-15
@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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Jos (10584)
Jos (10584) 2018-2-15
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

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