homework_2.py

# -*- coding: utf-8 -*-
def compute_mean(alist):

	sum_ = 0
	for idx in range(len(alist)):
		sum_ = sum_ + alist[idx]

	return sum_/float(len(alist))

def compute_median(alist):
	#alist = [3,2,1,5,7].sort()
	#alist = [1,2,3,5,7]

	#len(alist) = 6. len(alist)/2 , len(alist)/2 - 1
	alist.sort()

	if len(alist)%2 == 0: #even
		median_ = (alist[len(alist)/2] + alist[len(alist)/2 - 1])/2.0
		return median_
	else: # odd
		return alist[len(alist)/2]


def compute_mode(alist):
	alist.sort()
	# alist = [1,1,1,1,1,3,3,3,7,7, 9,9,9,9,9,9,9]
	mode_ = -1 # 5
	#모드숫자.
	mode_value = -1 # 3
	#모드 candidate 숫자.
	mode_candidate_count = 0 # 6
	#모드 candidate.
	for idx in range(len(alist)): 
		#initialization.
		if idx == 0:
			mode_candidate_count += 1

		# 이전 원소와 같다면 증가. 
		elif alist[idx] == alist[idx-1]:
			mode_candidate_count += 1
			if idx == len(alist)-1 and mode_candidate_count > mode_:
				mode_value = alist[idx-1]
				mode_ = mode_candidate_count
		#이전 원소와 다르다면. 모드인지 판정.
		else:

			#판정.
			if mode_candidate_count > mode_:
				#모드로 셋팅.
				mode_value = alist[idx-1]
				mode_ = mode_candidate_count

			#다시 초기화.
			mode_candidate_count = 1
		print 'index = {0}\n'.format(idx)
		print alist[idx], mode_, mode_value, mode_candidate_count
	#return mode of this @alist
	return mode_value, mode_



def compute_mode_dictionary(alist):
	alist.sort()
	mode_dictionary = {}
	for idx in range(len(alist)):

		if alist[idx] not in mode_dictionary:
			mode_dictionary[alist[idx]] = 1
		else:
			mode_dictionary[alist[idx]] += 1

	max_ = -1
	mode_ = -1
	for key in mode_dictionary.keys():
		print key, mode_dictionary[key]
		if mode_dictionary[key] > max_:
			max_ = mode_dictionary[key]
			mode_ = key

	return mode_, max_