我正在尝试使用朴素贝叶斯进行心脏病预测计划。当我完成分类器时,交叉验证显示平均准确度为80%但是当我尝试对给定样本进行预测时,预测完全错误!数据集是来自UCI存储库的心脏病数据集,它包含303个样本。有两个类0:健康和1:生病,当我尝试对数据集中的样本进行预测时,它不会预测其真实值,除非极少数样本。这是代码:
import pandas as pd
import numpy as np
from sklearn.naive_bayes import GaussianNB
from sklearn.model_selection import cross_val_score, train_test_split
from sklearn.preprocessing import Imputer, StandardScaler
class Predict:
def Read_Clean(self,dataset):
header_row = ['Age', 'Gender', 'Chest_Pain', 'Resting_Blood_Pressure', 'Serum_Cholestrol',
'Fasting_Blood_Sugar', 'Resting_ECG', 'Max_Heart_Rate',
'Exercise_Induced_Angina', 'OldPeak',
'Slope', 'CA', 'Thal', 'Num']
df = pd.read_csv(dataset, names=header_row)
df = df.replace('[?]', np.nan, regex=True)
df = pd.DataFrame(Imputer(missing_values='NaN', strategy='mean', axis=0)
.fit_transform(df), columns=header_row)
df = df.astype(float)
return df
def Train_Test_Split_data(self,dataset):
Y = dataset['Num'].apply(lambda x: 1 if x > 0 else 0)
X = dataset.drop('Num', axis=1)
validation_size = 0.20
seed = 42
X_train, X_test, Y_train, Y_test = train_test_split(X, Y, test_size=validation_size, random_state=seed)
return X_train, X_test, Y_train, Y_test
def Scaler(self, X_train, X_test):
scaler = StandardScaler()
X_train = scaler.fit_transform(X_train)
X_test = scaler.transform(X_test)
return X_train, X_test
def Cross_Validate(self, clf, X_train, Y_train, cv=5):
scores = cross_val_score(clf, X_train, Y_train, cv=cv, scoring='f1')
score = scores.mean()
print("CV scores mean: %.4f " % (score))
return score, scores
def Fit_Score(self, clf, X_train, Y_train, X_test, Y_test, label='x'):
clf.fit(X_train, Y_train)
fit_score = clf.score(X_train, Y_train)
pred_score = clf.score(X_test, Y_test)
print("%s: fit score %.5f, predict score %.5f" % (label, fit_score, pred_score))
return pred_score
def ReturnPredictionValue(self, clf, sample):
y = clf.predict([sample])
return y[0]
def PredictionMain(self, sample, dataset_path='dataset/processed.cleveland.data'):
data = self.Read_Clean(dataset_path)
X_train, X_test, Y_train, Y_test = self.Train_Test_Split_data(data)
X_train, X_test = self.Scaler(X_train, X_test)
self.NB = GaussianNB()
self.Fit_Score(self.NB, X_train, Y_train, X_test, Y_test, label='NB')
self.Cross_Validate(self.NB, X_train, Y_train, 10)
return self.ReturnPredictionValue(self.NB, sample)
当我跑步时:
if __name__ == '__main__':
sample = [41.0, 0.0, 2.0, 130.0, 204.0, 0.0, 2.0, 172.0, 0.0, 1.4, 1.0, 0.0, 3.0]
p = Predict()
print "Prediction value: {}".format(p.PredictionMain(sample))
结果是:
NB:健康评分0.84711,预测评分0.83607,CV评分平均值:0.8000
预测值:1
我得到1而不是0(此样本已经是数据集样本之一)。 我为数据集中的多个样本做了这个,大部分时间我都得到错误的结果,好像精度不是80%!
任何帮助将不胜感激。 提前谢谢。
修改 使用Pipeline解决问题。最终的代码是:
import pandas as pd
import numpy as np
from sklearn.naive_bayes import GaussianNB
from sklearn.model_selection import cross_val_score, train_test_split
from sklearn.preprocessing import Imputer, StandardScaler, OneHotEncoder
from sklearn.pipeline import Pipeline
class Predict:
def __init__(self):
self.X = []
self.Y = []
def Read_Clean(self,dataset):
header_row = ['Age', 'Gender', 'Chest_Pain', 'Resting_Blood_Pressure', 'Serum_Cholestrol',
'Fasting_Blood_Sugar', 'Resting_ECG', 'Max_Heart_Rate',
'Exercise_Induced_Angina', 'OldPeak',
'Slope', 'CA', 'Thal', 'Num']
df = pd.read_csv(dataset, names=header_row)
df = df.replace('[?]', np.nan, regex=True)
df = pd.DataFrame(Imputer(missing_values='NaN', strategy='mean', axis=0)
.fit_transform(df), columns=header_row)
df = df.astype(float)
return df
def Split_Dataset(self, df):
self.Y = df['Num'].apply(lambda x: 1 if x > 0 else 0)
self.X = df.drop('Num', axis=1)
def Create_Pipeline(self):
estimators = []
estimators.append(('standardize', StandardScaler()))
estimators.append(('bayes', GaussianNB()))
model = Pipeline(estimators)
return model
def Cross_Validate(self, clf, cv=5):
scores = cross_val_score(clf, self.X, self.Y, cv=cv, scoring='f1')
score = scores.mean()
print("CV scores mean: %.4f " % (score))
def Fit_Score(self, clf, label='x'):
clf.fit(self.X, self.Y)
fit_score = clf.score(self.X, self.Y)
print("%s: fit score %.5f" % (label, fit_score))
def ReturnPredictionValue(self, clf, sample):
y = clf.predict([sample])
return y[0]
def PredictionMain(self, sample, dataset_path='dataset/processed.cleveland.data'):
print "dataset: "+ dataset_path
data = self.Read_Clean(dataset_path)
self.Split_Dataset(data)
self.model = self.Create_Pipeline()
self.Fit_Score(self.model, label='NB')
self.Cross_Validate(self.model, 10)
return self.ReturnPredictionValue(self.model, sample)
现在对问题中的同一样本进行预测会返回[0],这是真正的值。实际上通过运行以下方法:
def CheckTrue(self):
clf = self.Create_Pipeline()
out = cross_val_predict(clf, self.X, self.Y)
p = [out == self.Y]
c = 0
for i in range(303):
if p[0][i] == True:
c += 1
print "Samples with true values: {}".format(c)
我使用管道代码获得249个真实样本,而之前我只有150个。
答案 0 :(得分:2)
您没有将StandardScaler应用于样本。分类器需要在StandardScaler.transform输出上训练的缩放数据,但样本的缩放方式与训练中的相同。
手动组合多个步骤(缩放,预处理,分类)时很容易出错。为避免此类问题,最好使用scikit-learn Pipeline。