MATLAB Functions

Array dimensions

d = size(X)
[m,n] = size(X)
m = size(X,dim)
[d1,d2,d3,...,dn] = size(X)

Description

d = size(X)

returns the sizes of each dimension of array X in a vector d with ndims(X) elements.

[m,n] = size(X)

returns the size of matrix X in variables m and n.

m = size(X,dim)

returns the size of the dimension of X specified by scalar dim.

[d1,d2,d3,...,dn] = size(X)

returns the sizes of the various dimensions of array X in separate variables.

If the number of output arguments n does not equal ndims(X), then:


If `n > ndims(X)`	Ones are returned in the "extra" variables `dndims(X)+1` through `dn`.
If `n < ndims(X)`	The final variable `dn` contains the product of the sizes of all the "remaining" dimensions of `X,` that is, dimensions `n+1` through `ndims(X)`.

Examples

The size of the second dimension of rand(2,3,4) is 3.

m = size(rand(2,3,4),2)

m =
     3

Here the size is output as a single vector.

d = size(rand(2,3,4))

d =
     2     3     4

Here the size of each dimension is assigned to a separate variable.

[m,n,p] = size(rand(2,3,4))
m =
     2

n =
     3

p =
     4

If X = ones(3,4,5), then

[d1,d2,d3] = size(X)

d1 =        d2 =     d3 =
    3             4      5

but when the number of output variables is less than ndims(X):

[d1,d2] = size(X)

d1 =        d2 =     
    3             20

The "extra" dimensions are collapsed into a single product.

If n > ndims(X), the "extra" variables all represent singleton dimensions:

[d1,d2,d3,d4,d5,d6] = size(X)

d1 =        d2 =         d3 =
    3             4          5

d4 =        d5 =         d6 =
     1            1          1