BUILT-IN MATHEMATICA SYMBOL

# Flatten

Flatten[list]
flattens out nested lists.

Flatten[list, n]
flattens to level n.

Flatten[list, n, h]

Flatten[list, {{s11, s12, ...}, {s21, s22, ...}, ...}]
flattens list by combining all levels to make each level i in the result.

## DetailsDetails

• Flatten "unravels" lists, effectively just deleting inner braces.
• Flatten[list, n] effectively flattens the top level in list n times.
• Flatten[f[e, ...]] flattens out subexpressions with head f.
• If the are matrices, Flatten[{{m11, m12}, {m21, m22}}, {{1, 3}, {2, 4}}] effectively constructs a single matrix from the "blocks" .
• Flatten[list, {{i1}, {i2}, ...}] effectively transposes levels in list, putting level in list at level k in the result. Note that the function Transpose in effect uses an inverse of this specification.
• Flatten flattens out levels in SparseArray objects just as in the corresponding ordinary arrays. »

## ExamplesExamplesopen allclose all

### Basic Examples (2)Basic Examples (2)

Flatten out lists at all levels:

 Out[1]=

Flatten only at level 1:

 Out[1]=