# full

## Purpose

Convert sparse matrices to full storage class.

## Synopsis

    A = full(S)

## Description

`A = full(S)` converts the storage of a matrix from sparse to full. If `A` is already full, `full(A)` returns `A`.

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 these computers, `sparse(X)` requires less storage than `full(X)`if the density, `nnz/(m*n)`, is less than one third. Operations on sparse matrices, however, require more execution time per element than those on full matrices, so density is 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    Elements     Bytes    Density  Complex

      A    200 by 200    40000    320000       Full    No
      S    200 by 200    26797    322364     0.6699    No

## See Also

    sparse

(c) Copyright 1994 by The MathWorks, Inc.