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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.
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, ReplacePart and MapAt. The form is different from the one used in Part.
The default level specification for Position is {0,
Infinity}, with Heads
->
True.
Position[
list
,
pattern
,
1
,
Heads
->
False] finds positions only of objects that appear as complete elements of list.
Level specifications are described in Section A.3.6.
Position[
expr
,
pattern
,
levspec
,
n
] gives the positions of the first n parts of expr which match the pattern.
See the Mathematica book: Section 1.8.5, Section 2.1.7, Section 2.2.4, Section 2.3.2.
See also: Cases, Count, StringPosition, ReplaceList, Insert, Delete.
Further Examples
The symbol c occurs in the third position of this list.
In[1]:= 
Out[1]= 
This gives the positions of the elements of the list that are manifestly powers.
In[2]:= 
Out[2]= 
The head of the expression (List in position 0) and the first two elements of the expression (a and Pi) have head Symbol.
In[3]:= 
Out[3]= 
In[4]:= 
Out[4]= 
In[5]:= 
THIS IS DOCUMENTATION FOR AN OBSOLETE PRODUCT. SEE THE DOCUMENTATION CENTER FOR THE LATEST INFORMATION. | | | |
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