numpy基础——numpy.argsort

numpy.argsort

numpy.argsort(a, axis=-1, kind=’quicksort’, order=None)

Returns the indices that would sort an array.
返回排序数组的索引。

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Perform an indirect sort along the given axis using the algorithm specified by the kind keyword. It returns an array of indices of the same shape as a that index data along the given axis in sorted order.
使用kind关键字指定的算法沿给定轴进行间接排序。 它按照排序的顺序返回与给定轴的索引数据相同形状的索引数组。

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Parameters:

a : array_like
Array to sort.

axis : int or None, optional
Axis along which to sort. The default is -1 (the last axis). If None, the flattened array is used.

kind : {‘quicksort’, ‘mergesort’, ‘heapsort’}, optional
Sorting algorithm.

order : str or list of str, optional
When a is an array with fields defined, this argument specifies which fields to compare first, second, etc. A single field can be specified as a string, and not all fields need be specified, but unspecified fields will still be used, in the order in which they come up in the dtype, to break ties.

Returns:

index_array : ndarray, int
Array of indices that sort a along the specified axis. If a is one-dimensional, a[index_array] yields a sorted a.

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Examples

One dimensional array:

返回的结果为 输入数组 元素从小到大 的索引

>>> x = np.array([3, 1, 2])>>> np.argsort(x)array([1, 2, 0])

Two-dimensional array:

>>> x = np.array([[0, 3], [2, 2]])>>> xarray([[0, 3],       [2, 2]])>>> np.argsort(x, axis=0)array([[0, 1],       [1, 0]])>>> np.argsort(x, axis=1)array([[0, 1],       [0, 1]])