# 姓 ? 名:耿大哥講算法
# 開發(fā)時(shí)間:2023/7/4 22:43
import matplotlib.pyplot as plt
from sklearn.metrics import precision_recall_curve,auc
import matplotlib;matplotlib.rc("font",family='Microsoft YaHei')

label=[0 ?,1 ?,0 ?,1 ?,1 ?,1 ?,0 ?,0 ?,1 ?,0 ?,0 ?,1]
score=[0.2,0.5,0.8,0.6,0.4,0.2,0.9,0.7,0.6,0.5,0.1,0.3]

if label.count(0)==len(label):print('真實(shí)類別全為負(fù)！')
elif label.count(1)==len(label):print('真實(shí)類別全為正！')
else:
? ?yuzhi=list(set(score))
? ?yuzhi.sort(reverse=True)
? ?if 1 not in yuzhi:yuzhi.insert(0,1)
? ?else:pass
? ?#不用工具包求Precision,Recall,yuzhi
? ?Recall,Precision=[],[]
? ?for k in yuzhi:
? ? ? ?TP,FP=0,0
? ? ? ?for i in range(len(label)):
? ? ? ? ? ?if label[i]==1 and score[i]>=k:TP+=1
? ? ? ? ? ?elif label[i]==0 and score[i]>=k:FP+=1
? ? ? ? ? ?else:pass
? ? ? ?Recall.append(TP/label.count(1))
? ? ? ?if TP+FP==0:Precision.append(1)
? ? ? ?else:Precision.append(TP/(TP+FP))
? ?#用工具包求Precision,Recall,yuzhi
? ?#Precision,Recall,yuzhi=precision_recall_curve(label,score)
? ?X,Y,jiaodian_x=Recall,Precision,[]
? ?for i in range(len(X)-1):
? ? ? ?if Y[i]>X[i] ? ?and Y[i+1]==X[i+1]:jiaodian_x.append(X[i+1])
? ? ? ?elif Y[i]>X[i] ?and Y[i+1]<X[i+1]:
? ? ? ? ? ?if X[i]==X[i+1]:jiaodian_x.append(X[i])
? ? ? ? ? ?else:jiaodian_x.append((X[i]*Y[i+1]-Y[i]*X[i+1])/(Y[i+1]-Y[i]-X[i+1]+X[i]))
? ? ? ?elif Y[i]==X[i] and Y[i+1]>X[i+1]:jiaodian_x.append(X[i])
? ? ? ?elif Y[i]==X[i] and Y[i+1]==X[i+1]:jiaodian_x.append(X[i+1]);jiaodian_x.append(X[i])
? ? ? ?elif Y[i]==X[i] and Y[i+1]<X[i+1]:jiaodian_x.append(X[i])
? ? ? ?elif Y[i]<X[i] ?and Y[i+1]>X[i+1]:
? ? ? ? ? ?if X[i]==X[i+1]:jiaodian_x.append(X[i])
? ? ? ? ? ?else:jiaodian_x.append((X[i]*Y[i+1]-Y[i]*X[i+1])/(Y[i+1]-Y[i]-X[i+1]+X[i]))
? ? ? ?elif Y[i]<X[i] ?and Y[i+1]==X[i+1]:jiaodian_x.append(X[i+1])
? ? ? ?else:pass
? ?jiaodian_x=list(set(jiaodian_x))
? ?plt.plot(X,Y,'b*-',label='PR曲線(AP='+str('%.3f'%auc(X,Y))+')')
? ?for i in jiaodian_x:plt.text(i-0.05,i+0.05,'%.3f'%i)
? ?plt.plot([0,1],[0,1],'*--',color='black',label='45°線')
? ?plt.plot(jiaodian_x,jiaodian_x,'ro')
? ?plt.xlabel('Recall');plt.ylabel('Precision');plt.legend();plt.show()