对二分类模型采用十折交叉验证评估

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14、对二分类模型采用十折交叉验证评估

#导入必要的包
import torch 
import torch.nn as nn
from torch.utils.data import TensorDataset,DataLoader
from torch.nn import init
import torch.optim as optim
from sklearn.model_selection import train_test_split
import numpy as np
import matplotlib.pyplot as plt

#创建数据集
num_inputs,num_example = 200,10000
x1 = torch.normal(2,2,(num_example,num_inputs))
y1 = torch.ones((num_example,1))
x2 = torch.normal(-2,2,(num_example,num_inputs))
y2 = torch.zeros((num_example,1))
x_data = torch.cat((x1,x2),dim=0)
y_data = torch.cat((y1,y2),dim = 0)
#train_x,test_x,train_y,test_y = train_test_split(x_data,y_data,shuffle=True,test_size=0.3,stratify=y_data)

#定义数据迭代器
batch_size = 256
train_dataset = TensorDataset(train_x,train_y)
train_iter = DataLoader(
    dataset = train_dataset,
    shuffle = True,
    num_workers = 0,
    batch_size = batch_size
)
test_dataset = TensorDataset(test_x,test_y)
test_iter = DataLoader(
    dataset = test_dataset,
    shuffle = True,
    num_workers = 0,
    batch_size = batch_size
)

#定义模型
num_input,num_hidden,num_output = 200,256,1
class net(nn.Module):
    def __init__(self,num_input,num_hidden,num_output):
        super(net,self).__init__()
        self.linear1 = nn.Linear(num_input,num_hidden,bias =False)
        self.linear2 = nn.Linear(num_hidden,num_output,bias=False)
    def forward(self,input):
        out = self.linear1(input)
        out = self.linear2(out)
        return out

model = net(num_input,num_hidden,num_output)
print(model)

net(
  (linear1): Linear(in_features=200, out_features=256, bias=False)
  (linear2): Linear(in_features=256, out_features=1, bias=False)
)

#初始化参数
for param in model.parameters():
    init.normal_(param,mean=0,std=0.001)

#定义训练函数
lr = 0.001
loss = nn.BCEWithLogitsLoss()
optimizer = optim.SGD(model.parameters(),lr)
def train(net,train_iter,test_iter,loss,num_epochs,batch_size):
    train_ls,test_ls,train_acc,test_acc = [],[],[],[]
    for epoch in range(num_epochs):
        train_ls_sum,train_acc_sum,n = 0,0,0
        for x,y in train_iter:
            y_pred = model(x)
            l = loss(y_pred,y)
            optimizer.zero_grad()
            l.backward()
            optimizer.step()
            train_ls_sum +=l.item()
            train_acc_sum += (((y_pred>0.5)==y)+0.0).sum().item()
            n += y_pred.shape[0]
        train_ls.append(train_ls_sum)
        train_acc.append(train_acc_sum/n)
        
        test_ls_sum,test_acc_sum,n = 0,0,0
        for x,y in test_iter:
            y_pred = model(x)
            l = loss(y_pred,y)
            test_ls_sum +=l.item()
            test_acc_sum += (((y_pred>0.5)==y)+0.0).sum().item()
            n += y_pred.shape[0]
        test_ls.append(test_ls_sum)
        test_acc.append(test_acc_sum/n)
        print('epoch %d, train_loss %.6f,test_loss %f, train_acc %.6f,test_acc %f'
              %(epoch+1, train_ls[epoch],test_ls[epoch], train_acc[epoch],test_acc[epoch]))
    return train_ls[epoch],test_ls[epoch],train_acc[epoch],test_acc[epoch]

#定义获取每折的训练集测试集数据的函数
def get_kfold_data(k, i, X, y):
    fold_size = X.shape[0] // k
    
    val_start = i * fold_size
    if i != k - 1:
        val_end = (i + 1) * fold_size
        X_valid, y_valid = X[val_start:val_end], y[val_start:val_end]
        X_train = torch.cat((X[0:val_start], X[val_end:]), dim = 0)
        y_train = torch.cat((y[0:val_start], y[val_end:]), dim = 0)
    else:
        X_valid, y_valid = X[val_start:], y[val_start:]
        X_train = X[0:val_start]
        y_train = y[0:val_start]
        
    return X_train, y_train, X_valid, y_valid

#定义多折交叉验证函数
def k_fold(k, X, y):
    
    train_loss_sum, valid_loss_sum = 0, 0
    train_acc_sum, valid_acc_sum = 0, 0
    
    data = []
    train_loss_to_data = []
    valid_loss_to_data = []
    train_acc_to_data = []
    valid_acc_to_data = []
    
    
    for i in range(k):
        print('第', i + 1,'折验证结果')
        X_train, y_train, X_valid, y_valid = get_kfold_data(k, i, X, y)
        dataset = Data.TensorDataset(X_train, y_train)  
        train_iter = Data.DataLoader(  
            dataset=dataset, # torch TensorDataset format  
            batch_size=batch_size, # mini batch size  
            shuffle=True, # 是否打乱数据 (训练集一般需要进行打乱)  
            num_workers=0, # 多线程来读数据， 注意在Windows下需要设置为0  
        )  
        # 将测试数据的特征和标签组合  
        dataset = Data.TensorDataset(X_valid, y_valid)  
        # 把 dataset 放入 DataLoader  
        test_iter = Data.DataLoader(  
            dataset=dataset, # torch TensorDataset format  
            batch_size=batch_size, # mini batch size  
            shuffle=True, # 是否打乱数据 
            num_workers=0, # 多线程来读数据， 注意在Windows下需要设置为0  
        )
        train_loss, val_loss, train_acc, val_acc = train(model,train_iter,test_iter,loss,num_epochs,batch_size)
        
        train_loss_to_data.append(train_loss)
        valid_loss_to_data.append(val_loss)
        train_acc_to_data.append(train_acc)
        valid_acc_to_data.append(val_acc)
        
        train_loss_sum += train_loss
        valid_loss_sum += val_loss
        train_acc_sum += train_acc
        valid_acc_sum += val_acc
    
    print('\n','最终k折交叉验证结果：')
    
    print('average train loss:{:.4f}, average train accuracy:{:.3f}%%'.format(train_loss_sum/k, train_acc_sum/k*100))
    print('average valid loss:{:.4f}, average valid accuracy:{:.3f}%%'.format(valid_loss_sum/k, valid_acc_sum/k*100))
    
    data.append(train_loss_to_data)
    data.append(valid_loss_to_data)
    data.append(train_acc_to_data)
    data.append(valid_acc_to_data)
    
    return data

#训练次数和学习率
num_epochs = 10
k = 10

#开始十折交叉验证
data = k_fold(k, x_data, y_data)

#导入绘制表格需要的包
import pandas as pd
import numpy as np
import os

#定义数据框架
name = []
for i in range(k):
    name.append("第"+str(i+1)+"折")
dataframe = {"name": name,
        "train_loss": data[0],
        "valid_loss": data[1],
        "train_acc": data[2],
        "loss_acc": data[3],}
frame = pd.DataFrame(dataframe)
frame.to_csv("./前馈神经网络十折交叉验证模型_二分类.csv", index=False)

#显示表格
pd.read_csv("./前馈神经网络十折交叉验证模型_二分类.csv")