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Count
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Count

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Count[list,pattern]

gives the number of elements in list that match pattern.

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Count[expr,pattern,levelspec]

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

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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].
  • Parallelize[Count[list,pattern]] computes Count[list,pattern] in parallel on all subkernels. »

Examples

open allclose all

Basic Examples  (4)Summary of the most common use cases

Count how many times b occurs:

In[1]:=1
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https://wolfram.com/xid/0deimq-b2q8pr
Out[1]=1

Count powers of x in an Association:

In[1]:=1
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https://wolfram.com/xid/0deimq-epmylo
Out[1]=1

Count powers of x on all levels:

In[1]:=1
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https://wolfram.com/xid/0deimq-ciqja1
Out[1]=1

Count symbols:

In[1]:=1
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https://wolfram.com/xid/0deimq-b785i8
Out[1]=1

Scope  (5)Survey of the scope of standard use cases

Count works with patterns:

In[1]:=1
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https://wolfram.com/xid/0deimq-guo8df
Out[1]=1

Count the number of elements not matching b:

In[1]:=1
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https://wolfram.com/xid/0deimq-c3tzzz
Out[1]=1

Count occurrences of b down to level 2:

In[1]:=1
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https://wolfram.com/xid/0deimq-evs45m
Out[1]=1

Count occurrences at level 2 only:

In[2]:=2
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https://wolfram.com/xid/0deimq-71g59o
Out[2]=2

Count all numeric expressions appearing as part of a larger expression:

In[1]:=1
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https://wolfram.com/xid/0deimq-25qk3n
Out[1]=1

A numeric level specification does not include level zero:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-egr7cw
Out[1]=1

Use a two-element list to explicitly include level zero:

In[2]:=2
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https://wolfram.com/xid/0deimq-qwiord
Out[2]=2

Generalizations & Extensions  (1)Generalized and extended use cases

Count works with any head, not just List:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-fyvpsm
Out[1]=1

Options  (1)Common values & functionality for each option

Heads  (1)

By default, expressions appearing as heads are not counted:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-hn26kn
Out[1]=1

Use the option Heads->True to include them:

In[2]:=2
✖
https://wolfram.com/xid/0deimq-8f4ejm
Out[2]=2

Applications  (3)Sample problems that can be solved with this function

Count the total number of symbols in an expression:

In[1]:=1
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https://wolfram.com/xid/0deimq-bds8t4
Out[1]=1

Count the total number of elements greater than 0.5:

In[1]:=1
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https://wolfram.com/xid/0deimq-7o0xq9
Out[1]=1

Count the number of rows whose first element is 1:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-h8oexq
Out[1]=1

Properties & Relations  (5)Properties of the function, and connections to other functions

Count returns the length of the result given by Cases:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-yrgdlg
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0deimq-ghayt4
Out[2]=2

Count returns the length of the result given by Position:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-dv934f
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0deimq-8sqw2y
Out[2]=2

A count at level {0} is effectively a numericized version of MatchQ:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-19ze7g
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0deimq-lqwcl
Out[2]=2

For most expressions, LeafCount equals the count matching Blank[] at level {-1}:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-wyy4g
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0deimq-jt63cw
Out[2]=2

Count treats Rational and Complex as atoms:

In[3]:=3
✖
https://wolfram.com/xid/0deimq-649t0c
Out[3]=3
In[4]:=4
✖
https://wolfram.com/xid/0deimq-9q8uup
Out[4]=4

LeafCount counts Rational and Complex numbers using their FullForm:

In[5]:=5
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https://wolfram.com/xid/0deimq-14u8xv
In[6]:=6
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https://wolfram.com/xid/0deimq-6c2vq
Out[6]=6

Compute Count in parallel:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-k6j9nd
Out[1]=1

Possible Issues  (1)Common pitfalls and unexpected behavior

Count looks for matches based on patterns, which may not be the same as numerical equality:

In[1]:=1
✖
https://wolfram.com/xid/0deimq-srm
Out[1]=1

Write a pattern using Condition to force searching based on numerical equality:

In[2]:=2
✖
https://wolfram.com/xid/0deimq-1u062z
Out[2]=2
Wolfram Research (1988), Count, Wolfram Language function, https://reference.wolfram.com/language/ref/Count.html (updated 2014).
✖
Wolfram Research (1988), Count, Wolfram Language function, https://reference.wolfram.com/language/ref/Count.html (updated 2014).

Text

Wolfram Research (1988), Count, Wolfram Language function, https://reference.wolfram.com/language/ref/Count.html (updated 2014).

✖
Wolfram Research (1988), Count, Wolfram Language function, https://reference.wolfram.com/language/ref/Count.html (updated 2014).

CMS

Wolfram Language. 1988. "Count." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/Count.html.

✖
Wolfram Language. 1988. "Count." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/Count.html.

APA

Wolfram Language. (1988). Count. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Count.html

✖
Wolfram Language. (1988). Count. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Count.html

BibTeX

@misc{reference.wolfram_2025_count, author="Wolfram Research", title="{Count}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/Count.html}", note=[Accessed: 06-April-2025 ]}

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@misc{reference.wolfram_2025_count, author="Wolfram Research", title="{Count}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/Count.html}", note=[Accessed: 06-April-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_count, organization={Wolfram Research}, title={Count}, year={2014}, url={https://reference.wolfram.com/language/ref/Count.html}, note=[Accessed: 06-April-2025 ]}

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@online{reference.wolfram_2025_count, organization={Wolfram Research}, title={Count}, year={2014}, url={https://reference.wolfram.com/language/ref/Count.html}, note=[Accessed: 06-April-2025 ]}