MATLAB Function Reference |

Convert sparse matrix to full matrix

**Syntax**

**Description**

```
A = full(S)
```

converts a sparse matrix `S`

to full storage organization. If `S`

is a full matrix, it is left unchanged. If `A`

is full, `issparse(A)`

is `0`

.

**Remarks**

Let `X`

be an `m`

-by-`n`

matrix with `nz`

`=`

`nnz(X)`

nonzero entries. Then `full(X)`

requires space to store `m*n`

real numbers while `sparse(X)`

requires space to store `nz`

real numbers and `(nz+n)`

integers.

On most computers, a real number requires twice as much storage as an integer. On such computers, `sparse(X)`

requires less storage than `full(X)`

if the density, `nnz/prod(size(X))`

, is less than one third. Operations on sparse matrices, however, require more execution time per element than those on full matrices, so density should be considerably less than two-thirds before sparse storage is used.

**Examples**

Here is an example of a sparse matrix with a density of about two-thirds. `sparse(S)`

and `full(S)`

require about the same number of bytes of storage.

S = sparse(+(rand(200,200) < 2/3)); A = full(S); whos Name Size Bytes Class A 200X200 320000 double array S 200X200 318432 double array (sparse)

**See Also**

ftell | fullfile |