Wolfram Language & System 10.0 (2014)|Legacy Documentation

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gives the number of elements in list that match pattern.

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

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

Details and OptionsDetails 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 through Infinity
    {n}level n only
    {n1,n2}levels through
  • The default value for levelspec in Count is .
  • 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].
Introduced in 1988
| Updated in 2014