BUILT-IN MATHEMATICA SYMBOL

# Position

Position[expr, pattern]
gives a list of the positions at which objects matching pattern appear in expr.

Position[expr, pattern, levelspec]
finds only objects that appear on levels specified by levelspec.

Position[expr, pattern, levelspec, n]
gives the positions of the first n objects found.

## Details and OptionsDetails and Options

• Position[expr, pattern] tests all the subparts of expr in turn to try and find ones that match pattern.
• Position returns a list of positions in a form suitable for use in Extract, ReplacePart, and MapAt. The form is different from the one used in Part.
• The default level specification for Position is {0, Infinity}, with .
• A part specification returned by Position represents the whole of expr.
• Position[list, pattern, {1}, Heads->False] finds positions only of objects that appear as complete elements of list.
• Position uses standard level specifications:
•  n levels through n Infinity levels through Infinity {n} level n only {n1,n2} levels through
• A positive level n consists of all parts of expr specified by n indices.
• A negative level -n consists of all parts of expr with depth n.
• Level corresponds to the whole expression.
• With the default option setting , Position includes heads of expressions, and their parts.
• Position traverses expressions in depth-first order, yielding lists of indices in lexicographic order.

## ExamplesExamplesopen allclose all

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

Find the positions at which occurs:

 Out[1]=
 Out[2]=

Find all positions at which to any power appears:

 Out[1]=

Find only those down to level 2:

 Out[2]=