Python 从numpy数组中随机选择
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Randomly select from numpy array
提问by scutnex
I have two related numpy arrays, Xand y. I need to select nrandom rows from Xand store this in an array, the corresponding yvalue and the appends to it the index of the points randomly selected.
我有两个相关的 numpy 数组，X和y. 我需要从中选择n随机行X并将其存储在一个数组中，相应的y值并将随机选择的点的索引附加到它。
I have another array indexwhich stores a list of index which I dont want to sample.
我有另一个数组index，它存储我不想采样的索引列表。
How can I do this?
我怎样才能做到这一点？
Sample data:
样本数据：
index = [2,3]
X = np.array([[0.3,0.7],[0.5,0.5] ,[0.2,0.8], [0.1,0.9]])
y = np.array([[0], [1], [0], [1]])
If these X's were randomly selected (where n=2):
如果这些X是随机选择的（其中n=2）：
randomylSelected = np.array([[0.3,0.7],[0.5,0.5]])
the desired output would be:
所需的输出是：
index = [0,1,2,3]
randomlySelectedY = [0,1]
How can I do this?
我怎样才能做到这一点？
回答by MSeifert
You can create random indices with np.random.choice:
您可以使用以下方法创建随机索引np.random.choice：
n = 2 # for 2 random indices
index = np.random.choice(X.shape[0], n, replace=False)
Then you just need to index your arrays with the result:
然后你只需要用结果索引你的数组：
x_random = X[index]
y_random = Y[index]
回答by Alon Gouldman
just to wrap @MSeifert 's answer in a function:
只是为了将 @MSeifert 的答案包装在一个函数中：
def random_sample(arr: numpy.array, size: int = 1) -> numpy.array:
return arr[np.random.choice(len(arr), size=size, replace=False)]
useage:
用途：
randomlySelectedY = random_sample(Y)
