How do I resize a matrix in MATLAB?

matlab matrix reshape

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Suppose I had a 1-by-12 matrix and I wanted to resize it to a 4-by-3 matrix. How could I do this?

My current solution is kind of ugly:

for n = 1:(length(mat)/3)
    out(n,1:3) = mat( ((n-1)*3 + 1):((n-1)*3 + 3) );
end

Is there a better way to do this?

Автор: bastibe Источник Размещён: 27.04.2009 01:51

Ответы (3)


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Try the RESHAPE function:

A = (1-by-12 matrix);
B = reshape(A,4,3);

Note that the matrix B will be filled with elements from A in a columnwise fashion (i.e. columns will be filled from top to bottom, moving left to right).

Example:

>> A = 1:12;
>> B = reshape(A,4,3)

B =

     1     5     9
     2     6    10
     3     7    11
     4     8    12
Автор: gnovice Размещён: 27.04.2009 01:52

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to extend gnovice's solution:

If you need a different order of matrix construction, use transpose (the ' operator) or permute() to change the dimension ordering after you have called reshape().

Автор: Jason S Размещён: 27.04.2009 02:02

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Решение

reshape is of course the proper solution, as stated by @gnovice.

A nice feature of reshape is that it allows this:

A = 1:12;
B = reshape(A,4,[]);
B =
     1     5     9
     2     6    10
     3     7    11
     4     8    12

So if you don't know how many columns there will be, reshape will compute it for you. Likewise, reshape will fill in the number of rows, if you leave that out.

C = reshape(A,[],4)
C =
     1     4     7    10
     2     5     8    11
     3     6     9    12
Автор: user85109 Размещён: 27.04.2009 02:14
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