MATLAB Understanding size() Function for 2x2 Matrices

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The function size(A,n) in MATLAB returns the length of matrix A along its nth dimension. For a 2x2 matrix, size(A,1) and size(A,2) both equal 2, indicating it has 2 rows and 2 columns. For any n greater than 2, size(A,n) equals 1, as the matrix does not extend beyond its two dimensions. The discussion clarifies that the first dimension refers to the number of rows and the second to the number of columns. There is some debate about the definition of dimensions, with one perspective suggesting that a 2x2 matrix could be viewed as a single entry in a list of such matrices, which explains why higher dimensions return a length of 1. There is also a suggestion that MATLAB could return 0 for higher dimensions instead of 1, which could simplify understanding.
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What does the function size(A,1) and size(A,2) and size(A,32) mean for a random (in other words, any) 2 by 2 matrix?
 
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size(A,n) returns the length along the nth dimension of the matrix A.

This means that for a 2x2 matrix (i.e a 2D matrix) for n>2 we have that size(A,n)=1 but for n=1,2 size(A,n)=2 since it is only in the first two dimensions that the matrix has any entries.
 
cpt_carrot said:
size(A,n) returns the length along the nth dimension of the matrix A.

This means that for a 2x2 matrix (i.e a 2D matrix) for n>2 we have that size(A,n)=1 but for n=1,2 size(A,n)=2 since it is only in the first two dimensions that the matrix has any entries.

What is the nth dimension of a matrix A? How is dimension defined?

Isn't it the case that the dimension of a 2x2 matrix is 4?

Or are you referring to that dimension 1 of a matrix is the number of rows. 2nd dimension of a matrix is the column size? But what is the 3rd dimension of a matrix?
 
Last edited:
In this context, the first "dimension" is the number of columns, and the second "dimension" is the number of rows.

A 2x2 matrix can be thought of as a single entry in a 1-element long list of 2x2 matrices, which is why the higher "dimensions" in MATLAB all have length 1.

- Warren
 
chroot said:
In this context, the first "dimension" is the number of columns, and the second "dimension" is the number of rows.

A 2x2 matrix can be thought of as a single entry in a 1-element long list of 2x2 matrices, which is why the higher "dimensions" in MATLAB all have length 1.

- Warren

I think it's the opposite after trying it on a 3 by 2 matrix. First dimension is the number of rows and second dimension is the number of columns.

However, it would make more sense if MATLAB gave 0 as the size of the higher dimensions of matrices.
 

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