Aggregate pattern: Difference between revisions

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{{Short description|Concepts in statistics and computer science}}

An '''Aggregate pattern''' can refer to concepts in either statistics or computer programming. Both uses deal with considering a large case as composed of smaller, simpler, pieces.

{{one source |date=March 2024}}

An '''Aggregate pattern''' can refer to concepts in either statistics or computer programming. Both uses dealsimplify withcomplexity considering a large case as composed ofinto smaller, simpler, piecesparts.

== 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">

<pre>

def fibonacci(n: int):

mylist = ['apples','oranges','milk','eggs','flour']

a, b = b0, a+b1

count += 10

for item in mylist:

while count < n:

print "Mom, we're out of " + item + "!"

count += 01

a, b = b, a + b

def fibonacci(n):

a,b = 0,1 yield a

count = 0

while count < n:

count += 1

a,b = b, a+b

yield a

for x in fibonacci(10):

print print(x)

def fibsum(n):

total = 0

for x in fibonacci(n):

total += x

return total

def fibsum_alt(n):

"Alternate implementation. demonstration that Python's built-in function sum() works with arbitrary iterators"

return sum(fibonacci(n))

def fibsum(n: int) -> int:

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

total = 0

for x in fibonacci(n):

total += x

return total

def averagefibsum_alt(gn: int) -> int:

"""

return float(sum(g))/len(g) #in Python 3.0 the cast to float will no longer be necessary

" Alternate implementation. demonstration that Python's built-in function sum() works with arbitrary iterators"

works with arbitrary iterators.

"""

return sum(fibonacci(n))

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

</pre>

def average(g) -> float:

Python hides essentially all of the details using the [http://www.python.org/doc/lib/typeiter.html 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.

return float(sum(g)) / len(g) #in In Python 3.0 the cast to float willis no longer be necessary

</syntaxhighlight>

Python hides essentially all of the details using the [httphttps://wwwdocs.python.org/doc3/liblibrary/typeiterstdtypes.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 ==

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[[Category:Software design patterns]]

[[Category:Articles with example PerlPython (programming language) code]]