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MapAt
MapAt[
f
,
expr
,
n
] applies f to the element at position n in expr. If n is negative, the position is counted from the end.
MapAt[
f
,
expr
,
i
,
j
, ... 
] applies f to the part of expr at position 
i
,
j
, ...  .
MapAt[
f
,
expr
,
,
, ... 
,
,
, ... 
, ... 
] applies f to parts of expr at several positions.
Example: MapAt[f,
a, b, c
, 2] .
MapAt[f,
a, b, c, d
,
1
,
4
].
MapAt[
f
,
expr
,
i
,
j
, ... 
] or MapAt[
f
,
expr
,
i
,
j
, ... 
] applies f to the part expr
[[
i
,
j
, ... ]].
MapAt[
f
,
expr
,
,
, ... 
,
,
, ... 
, ... 
] applies f to parts expr
[[
,
, ... ]], expr
[[
,
, ... ]], ... .
The list of positions used by MapAt is in the same form as is returned by the function Position.
MapAt applies f repeatedly to a particular part if that part is mentioned more than once in the list of positions.
Example: MapAt[f,
a, b, c
,
1
,
3
,
1
].
See the Mathematica book: Section 2.2.4.
See also: ReplacePart, Delete, FlattenAt.
Further Examples
This specifies that f is mapped across the list at position 2 only.
In[1]:= 
Out[1]= 
Here, f is mapped on the first position of the second element.
In[2]:= 
Out[2]= 
To avoid ambiguity, you must put each part specification in a list, even when it involves only one index.
In[3]:= 
Out[3]= 
THIS IS DOCUMENTATION FOR AN OBSOLETE PRODUCT. SEE THE DOCUMENTATION CENTER FOR THE LATEST INFORMATION. | | | |
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