Naive Bayes的Python实现
Naive Bayes的Python实现
明天考试，可以带电脑，先写好了程序，省的按计算器……直接上Python的源代码。[python]
#Naive Bayes
#Calculate the Prob. of class:cls
def P(data,cls_val,cls_name="class"):
cnt = 0.0
for e in data:
if e[cls_name] == cls_val:
cnt += 1
return cnt/len(data)
#Calculate the Prob(attr|cls)
def PT(data,cls_val,attr_name,attr_val,cls_name="class"):
cnt1 = 0.0
cnt2 = 0.0
for e in data:
if e[cls_name] == cls_val:
cnt1 += 1
if e[attr_name] == attr_val:
cnt2 += 1
return cnt2/cnt1
#Calculate the NB
def NB(data,test,cls_y,cls_n):
PY = P(data,cls_y)
PN = P(data,cls_n)
for key,val in test.items():
print key,val
PY *= PT(data,cls_y,key,val)
PN *= PT(data,cls_n,key,val)
return {cls_y:PY,cls_n:PN}
if __name__ == "__main__":
#data
data = [
{"outlook":"sunny", "temp":"hot", "humidity":"high", "wind":"weak", "class":"no" },
{"outlook":"sunny", "temp":"hot", "humidity":"high", "wind":"strong", "class":"no" },
{"outlook":"overcast", "temp":"hot", "humidity":"high", "wind":"weak", "class":"yes" },
{"outlook":"rain", "temp":"mild", "humidity":"high", "wind":"weak", "class":"yes" },
{"outlook":"rain", "temp":"cool", "humidity":"normal", "wind":"weak", "class":"yes" },
{"outlook":"rain", "temp":"cool", "humidity":"normal", "wind":"strong", "class":"no" },
{"outlook":"overcast", "temp":"cool", "humidity":"normal", "wind":"strong", "class":"yes" },
{"outlook":"sunny", "temp":"mild", "humidity":"high", "wind":"weak", "class":"no" },
{"outlook":"sunny", "temp":"cool", "humidity":"normal", "wind":"weak", "class":"yes" },
{"outlook":"rain", "temp":"mild", "humidity":"normal", "wind":"weak", "class":"yes" },
{"outlook":"sunny", "temp":"mild", "humidity":"normal", "wind":"strong", "class":"yes" },
{"outlook":"overcast", "temp":"mild", "humidity":"high", "wind":"strong", "class":"yes" },
{"outlook":"overcast", "temp":"hot", "humidity":"normal", "wind":"weak", "class":"yes" },
{"outlook":"rain", "temp":"mild", "humidity":"high", "wind":"strong", "class":"no" },
]
#calculate
print NB(data,{"outlook":"sunny","temp":"cool","humidity":"high","wind":"strong"},"yes","no")
[/python]
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