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:
•  n levels 1 through n Infinity levels 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 , 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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