DocumentationMathematicaBuilt-in FunctionsProgrammingFunctional Programming
Further Examples: MapAt
This specifies that f is mapped across the list at position only.
Here f is mapped on the second position of the first element.
To avoid ambiguity when there is more than one part specification, you must put each of them in a separate sublist.
Here is a matrix.
This replaces all the elements of the second row and the first element of the third row by zeros.