Count

Count[list,pattern]

gives the number of elements in list that match pattern.

Count[expr,pattern,levelspec]

gives the total number of subexpressions matching pattern that appear at the levels in expr specified by levelspec.

Count[pattern]

represents an operator form of Count that can be applied to an expression.

Details and Options

  • The first argument to Count need not have head List.
  • When used on an Association, Count tests only the values of elements, not their keys.
  • Count uses standard level specifications:
  • nlevels 1 through n
    Infinitylevels 1 through Infinity
    {n}level n only
    {n1,n2}levels n1 through n2
  • The default value for levelspec in Count is {1}.
  • A positive level n consists of all parts of expr specified by n indices.
  • A negative level -n consists of all parts of expr with depth n.
  • Level -1 consists of numbers, symbols and other objects that do not have subparts.
  • Level 0 corresponds to the whole expression.
  • With the option setting Heads->True, Count looks at heads of expressions and their parts.
  • Count[pattern][expr] is equivalent to Count[expr,pattern].

Examples

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Basic Examples  (4)

Count how many times b occurs:

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Count powers of x in an Association:

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Count powers of x on all levels:

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Count symbols:

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Scope  (5)

Generalizations & Extensions  (1)

Options  (1)

Applications  (3)

Properties & Relations  (4)

Possible Issues  (1)

See Also

Cases  Position  LeafCount  FreeQ  MatchQ  MemberQ  Select  SequenceCount  StringCount  BinCounts  Counts  Tally  Total

Tutorials

Introduced in 1988
(1.0)
| Updated in 2014
(10.0)