余弦相似性计算及python代码实现

A：西米喜欢健身

B：超超不爱健身，喜欢打游戏

step1:分词

A：西米／喜欢／健身

B：超超／不／喜欢／健身，喜欢／打／游戏

step2:列出两个句子的并集

西米／喜欢／健身／超超／不／打／游戏

step3:计算词频向量

A：[1,1,1,0,0,0,0]

B：[0,1,1,1,1,1,1]

step4:计算余弦值

 余弦值越大，证明夹角越小，两个向量越相似。

step5:python代码实现

import jieba
import jieba.analyse

def words2vec(words1=None, words2=None):
    v1 = []
    v2 = []
    tag1 = jieba.analyse.extract_tags(words1, withWeight=True)
    tag2 = jieba.analyse.extract_tags(words2, withWeight=True)
    tag_dict1 = {i[0]: i[1] for i in tag1}
    tag_dict2 = {i[0]: i[1] for i in tag2}
    merged_tag = set(tag_dict1.keys()) | set(tag_dict2.keys())
    for i in merged_tag:
        if i in tag_dict1:
            v1.append(tag_dict1[i])
        else:
            v1.append(0)
        if i in tag_dict2:
            v2.append(tag_dict2[i])
        else:
            v2.append(0)
    return v1, v2


def cosine_similarity(vector1, vector2):
    dot_product = 0.0
    normA = 0.0
    normB = 0.0
    for a, b in zip(vector1, vector2):
        dot_product += a * b
        normA += a ** 2
        normB += b ** 2
    if normA == 0.0 or normB == 0.0:
        return 0
    else:
        return round(dot_product / ((normA**0.5)*(normB**0.5)) * 100, 2)
	
def cosine(str1, str2):
    vec1, vec2 = words2vec(str1, str2)
    return cosine_similarity(vec1, vec2)

print(cosine('阿克苏苹果', '阿克苏苹果'))