size (MATLAB Functions)

Array dimensions

Syntax

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. If X is a scalar, which MATLAB regards as a 1-by-1 array, size(X) returns the vector [1 1].

[m,n] = size(X) returns the size of matrix X in separate 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), for n > 1, returns the sizes of the dimensions of the array X in the variables d1,d2,d3,...,dn, provided the number of output arguments n equals ndims(X). If n does not equal ndims(X), the following exceptions hold:

n < ndims(X)

di equals the size of the ith dimension of X for , but dn equals the product of the sizes of the remaining dimensions of X,that is, dimensions n through ndims(X).

n > ndims(X)
size returns ones in the "extra" variables, that is, those corresponding to ndims(X)+1 through n.

`n < ndims(X)`	`di` equals the size of the `i`th dimension of `X` for , but `dn` equals the product of the sizes of the remaining dimensions of `X,`that is, dimensions `n` through `ndims(X)`.
`n > ndims(X)`	`size` returns ones in the "extra" variables, that is, those corresponding to `ndims(X)+1` through `n`.

Note For a Java array, size returns the length of the Java array as the number of rows. The number of columns is always 1. For a Java array of arrays, the result describes only the top level array.

Examples

Example 1. 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

Example 2. 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

See Also

exist, length, numel, whos

sinh slice