数据基础处理-numpy

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本文详细介绍了 numpy 中的 argsort 函数，该函数用于返回能够将输入数组排序的索引数组。文章解释了如何通过指定参数来调整排序行为，并提供了一个使用示例。

numpy中argsort函数用法

>>> import numpy
>>> help(numpy.argsort)
Help on function argsort in module numpy.core.fromnumeric:

argsort(a, axis=-1, kind='quicksort', order=None)
Returns the indices that would sort an array.

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.

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.

X_train_reduced = X_train[X_train.columns.values[(np.argsort(importances)[::-1])[:5]]]

>>> import numpy
>>> help(numpy.argsort)
Help on function argsort in module numpy.core.fromnumeric:

argsort(a, axis=-1, kind='quicksort', order=None)
    Returns the indices that would sort an array.

    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.

    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.