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 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
(1.0)
| Updated in 2014
(10.0)