Position
Position[expr, pattern] gives a list of the positions at which objects matching pattern appear in expr.
Position[expr, pattern, levspec] finds only objects that appear on levels specified by levspec.
Position[expr, pattern, levspec, n] gives the positions of the first n objects found.
Example: Position[
1+x^2, 5, x^4
, x^_]
.
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 and ReplacePart. The form is different from the one used in Part.
The default level specification for Position is {0, Infinity}, with Heads -> True.
A part specification {} returned by Position represents the whole of expr.
Level specifications are described in Section A.3.6.
See The Mathematica Book on the web: Section 1.8.5, Section 2.1.7, Section 2.2.4 and Section 2.3.2.
See also: Cases, Count, Ordering, ReplaceList, Insert, Delete.
Further Examples
