ReplacePart

ReplacePart[expr,inew]
yields an expression in which the ^(th) part of expr is replaced by new.

ReplacePart[expr,{i1new1,i2new2,}]
replaces parts at positions by .

ReplacePart[expr,{i,j,}new]
replaces the part at position .

ReplacePart[expr,{{i1,j1,}new1,}]
replaces parts at positions by .

ReplacePart[expr,{{i1,j1,},}new]
replaces all parts at positions by new.

ReplacePart[inew]
represents an operator form of ReplacePart that can be applied to an expression.

Details and OptionsDetails and Options

  • Explicit negative part numbers count from the end. »
  • Part position specifications can be patterns.
  • Each pattern is effectively tested against each list of part numbers for parts in expr.
  • Patterns p (such as ) that are not explicitly lists are treated as {p}.
  • Patterns can include constructs such as , representing position specifications of variable lengths.
  • ReplacePart[expr,i:>new] can be used to replace a part without first evaluating it. With a rule such as , new is evaluated separately for each position that matches patt.
  • With the default option setting Heads->Automatic, a head is replaced only when the corresponding position specification is explicitly .
  • With Heads->True a head is replaced whenever the corresponding position specification matches .
  • Heads->False never replaces heads.
  • ReplacePart can be used on SparseArray objects.

ExamplesExamplesopen allclose all

Basic Examples  (5)Basic Examples  (5)

Replace part 3:

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Replace parts 2 and 5:

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Replace part of an array:

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Replace parts whose positions match a pattern:

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Replace parts in any expression:

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Introduced in 1991
(2.0)
| Updated in 2014
(10.0)
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