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Mathematica > Parts of Expressions >

Built-in Mathematica Symbol

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, {{i₁, j₁, ...}, {i₂, j₂, ...}, ...}]
applies f to parts of expr at several positions.

MapAt[f, expr, {i, j, ...}] or MapAt[f, expr, {{i, j, ...}}] applies f to the part expr[[i, j, ...]].

MapAt[f, expr, {{i₁, j₁, ...}, {i₂, j₂, ...}, ...}] applies f to parts expr[[i₁, j₁, ...]], expr[[i₂, j₂, ...]], .... »

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. »

Map f onto the part at position 2:

Map f onto multiple parts:

Map f onto a more deeply nested part: