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2025-02-12T02:53:20Z

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{{Short description|Concepts in statistics and computer science}}
{{one source |date=March 2024}}
An '''Aggregate pattern''' can refer to concepts in either statistics or computer programming. Both uses simplify complexity into smaller, simpler parts.

== Statistics ==
An aggregate pattern is an important statistical concept in many fields that rely on [[statistics]] to predict the behavior of large groups, based on the tendencies of subgroups to consistently behave in a certain way. It is particularly useful in [[sociology]], [[economics]], [[psychology]], and [[criminology]].

== Computer programming ==

In ''[[Design Patterns]]'', an aggregate is not a [[Software design pattern|design pattern]] but rather refers to an object such as a list, vector, or generator which provides an interface for creating [[iterator]]s. The following example code is in [[Python (programming language)|Python]].
<syntaxhighlight lang="python">
def fibonacci(n: int):
a, b = 0, 1
count = 0
while count < n:
count += 1
a, b = b, a + b
yield a

for x in fibonacci(10):
print(x)

def fibsum(n: int) -> int:
total = 0
for x in fibonacci(n):
total += x
return total

def fibsum_alt(n: int) -> int:
"""
Alternate implementation. demonstration that Python's built-in function sum()
works with arbitrary iterators.
"""
return sum(fibonacci(n))

myNumbers = [1, 7, 4, 3, 22]

def average(g) -> float:
return float(sum(g)) / len(g) # In Python 3 the cast to float is no longer be necessary
</syntaxhighlight>
Python hides essentially all of the details using the [https://docs.python.org/3/library/stdtypes.html#iterator-types iterator protocol]. Confusingly, ''[[Design Patterns]]'' uses "aggregate" to refer to the blank in the code <code>for x in ___:</code> which is unrelated to the term "aggregation".<ref>[[Design Patterns]], p. 22: "Aggregation implies that one object owns or is responsible for another object. ... Aggregation implies that an aggregate object and its owner have identical lifetimes."</ref> Neither of these terms refer to the statistical aggregation of data such as the act of adding up the Fibonacci sequence or taking the average of a list of numbers.

== See also ==
* [[Visitor pattern]]
* [[Template class]]
* [[Facade pattern]]
* [[Type safety]]
* [[Functional programming]]

== References ==
{{Reflist}}

[[Category:Software design patterns]]
[[Category:Articles with example Python (programming language) code]]

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Aggregate pattern - Revision history

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