Question

我正在尝试在不使用测试矩阵的库的情况下实现k交叉验证背后的逻辑。以某种方式，我的旋转矩阵无法正常工作。

我将k设为5。

X = np.matrix([[1,2,3,4,5],[7,8,9,4,5],[4,9,6,4,2],[9,5,1,2,3],[7,5,3,4,6]])
P = np.ones((5,5))
target = np.matrix([[1,2,3,4,5]]).T
#def k_fold(X,target,k):
r = X.shape[0]  
k=5
step = r//k  
last_row_train = step*(k-1) 

for i in range(5):
    X_train = X[0:last_row_train,:]
    tempX = X_train

    X_test = X[last_row_train:r,:]
    temp_X_test = X_test

    t_train = target[0:last_row_train,:]
    temp_t_train = t_train
    t_test = target[last_row_train:r,:]
    temp_test = t_test
    X[step:r,:] = tempX # On running this line, it changes the value of 
                        #  temp_X_test which is very weird and not
                        # supposed to happen 
    X[0:step,:] = temp_X_test 
    target[0:step,:] = temp_test
    target[step:r,:] = temp_t_train
    print (X)
    print (target)

Answer 1

tempX = X_train

此语句不会创建新变量tempX并为其分配X_train。它使变量名称tempX和X_train都指向同一对象。 tempX的任何更改都将反映在X_train中。这是代码中经常发生的问题。

当尝试进行这样的列表分配时，请使用以下代码。

tempX = X_train.copy()

这里是指向类似问题的链接，提供了更多解决方案。
How to clone or copy a list?

交叉验证在python中的实现

1 个答案: