weightedNumGenerator Namespace Reference

Return random numbers weighted by given probabilities. More...

Functions
def	genWeightedList (l, weights)
	Method 1 – given a list of of items and a list of probabilities, return a new list that contains int(100*prob[i]) duplicates of the i-th item. More...
def	genWeightedListD (d)
	Using a dictionary, instead of two lists. More...
def	weightedRand (seq)
	Return a random element from seq (same of choice from random). More...
def	weightedRand2 (l, weights)
	Method 2 – given list of items and a list of probabilities, which sum up to one, for example, 0.5 + 0.2 + 0.2 + 0.1 = 1.0. More...
def	weightedRandD (d)
	Using a dictionary. More...
def	main ()
	Main program for testing. More...

Detailed Description

Return random numbers weighted by given probabilities.

Author

Flavia e Paulo Roma

Since

16/06/2016

See also

http://programmers.stackexchange.com/questions/150616/return-random-list-item-by-its-weight

Function Documentation

genWeightedList()

def weightedNumGenerator.genWeightedList	(		l,
			weights
	)

Method 1 – given a list of of items and a list of probabilities, return a new list that contains int(100*prob[i]) duplicates of the i-th item.

Randomly select an item from that new list within the range [0, length(list)]

Parameters

l	list of items.
weights	list of probabilities.

Returns

a list of items with multiplicity given by its corresponding probability times 100 (minimum p=0.01).

Referenced by main().

genWeightedListD()

def weightedNumGenerator.genWeightedListD

(

d

)

Using a dictionary, instead of two lists.

Parameters

d	pairs of items,probabilities.

Returns

a list of items with multiplicity given by its corresponding probability times 100 (minimum p=0.01).

Referenced by main().

main()

def weightedNumGenerator.main

(

)

Main program for testing.

References genWeightedList(), genWeightedListD(), weightedRand(), weightedRand2(), and weightedRandD().

weightedRand()

def weightedNumGenerator.weightedRand

(

seq

)

Return a random element from seq (same of choice from random).

Parameters

seq	given sequence of items.

Returns

random item.

Referenced by main().

weightedRand2()

def weightedNumGenerator.weightedRand2	(		l,
			weights
	)

Method 2 – given list of items and a list of probabilities, which sum up to one, for example, 0.5 + 0.2 + 0.2 + 0.1 = 1.0.

Get a random number between 0 and the total weight (1.0).

• If the random number falls in the first slot, or weight[0] (which is 0.5 in the example), then choose the first item from the list.
• If it falls in the second slot, which is between weight[0] and weight[0] + weight[1], then select the second item from the list.
• For third item, the random number must fall in the third slot, which would be between weight[0] + weight[1] and weight[0] + weight[1] + weight[2],
• and the sequence goes on.

TODO - make method more efficient with quicksort

Parameters

l	list of items
weights	list of probabilities.

Returns

a random item weighted by given probabilities.

Referenced by main().

weightedRandD()

def weightedNumGenerator.weightedRandD

(

d

)

Using a dictionary.

Parameters

d	pairs of items,probabilities.

Returns

a random item weighted by given probabilities.

Referenced by main().