CODEWITHSUNDEEP
matlabmatrixreshape
Hugo
Hugo

Reputation: 347

How do I reshape a non-quadratic matrix?

I have a column vector A with dimensions (35064x1) that I want to reshape into a matrix with 720 lines and as many columns as it needs.

In MATLAB, it'd be something like this:

B = reshape(A,720,[])

in which B is my new matrix.

However, if I divide 35604 by 720, there'll be a remainder.

Ideally, MATLAB would go about filling every column with 720 values until the last column, which wouldn't have 720 values; rather, 504 values (48x720+504 = 35064).

Is there any function, as reshape, that would perform this task?

Since I am not good at coding, I'd resort to built-in functions first before going into programming.

Upvotes: 0

Views: 85

Answers (3)

karakfa
karakfa

Reputation: 67467

reshape preserves the number of elements but you achieve the same in two steps

b=zeros(720*ceil(35604/720),1); b(1:35604)=a;
reshape(b,720,[])

Upvotes: 3

Daniel
Daniel

Reputation: 36710

karakfa got the right idea, but some error in his code.

Fixing the errors and slightly simplifying it, you end up with:

B=nan(720,ceil(numel(a)/720));
B(1:numel(A))=A;

Create a matrix where A fits in and assingn the elemnent of A to the first numel(A) elements of the matrix.

An alternative implementation which is probably a bit faster but manipulates your variable b

%pads zeros at the end
A(720*ceil(numel(A)/720))=0;
%reshape
B=reshape(A,720,[]);

Upvotes: 0

Adriaan
Adriaan

Reputation: 18177

A = rand(35064,1);
NoCols = 720;
tmp = mod(numel(A),NoCols ); % get the remainder
tmp2 = NoCols -tmp;
B = reshape([A; nan(tmp2,1)],720,[]); % reshape the extended column

This first gets the remainder after division, and then subtract that from the number of columns to find the amount of missing values. Then create an array with nan (or zeros, whichever suits your purpose best) to pad the original and then reshape. One liner:

A = rand(35064,1);
NoCols = 720;
B = reshape([A; nan(NoCols-mod(numel(A),NoCols);,1)],720,[]);

Upvotes: 0

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