.shape []在"for i in range(Y.shape [0])"中有什么作用? [英] What does .shape[] do in "for i in range(Y.shape[0])"?
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问题描述
我正在尝试逐行细分程序. Y
是数据矩阵,但我找不到有关.shape[0]
确切功能的任何具体数据.
I'm trying to break down a program line by line. Y
is a matrix of data but I can't find any concrete data on what .shape[0]
does exactly.
for i in range(Y.shape[0]):
if Y[i] == -1:
该程序使用numpy,scipy,matplotlib.pyplot和cvxopt.
This program uses numpy, scipy, matplotlib.pyplot, and cvxopt.
推荐答案
numpy数组的shape
属性返回数组的尺寸.如果Y
具有n
行和m
列,则Y.shape
为(n,m)
.所以Y.shape[0]
是n
.
The shape
attribute for numpy arrays returns the dimensions of the array. If Y
has n
rows and m
columns, then Y.shape
is (n,m)
. So Y.shape[0]
is n
.
In [46]: Y = np.arange(12).reshape(3,4)
In [47]: Y
Out[47]:
array([[ 0, 1, 2, 3],
[ 4, 5, 6, 7],
[ 8, 9, 10, 11]])
In [48]: Y.shape
Out[48]: (3, 4)
In [49]: Y.shape[0]
Out[49]: 3
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