如何获得与0
最接近的n
值,类似于如何使用nsmallest()
获得最小的n值。例如,使用
series = pd.Series([-1.0,-0.75,-0.5,-0.25,0.25,0.5,0.75,1.0])
series
0 -1.00
1 -0.75
2 -0.50
3 -0.25
4 0.25
5 0.50
6 0.75
7 1.00
dtype: float64
例如n=4
,我想得到以下内容。
0 -0.25
1 0.25
2 -0.50
3 0.50
dtype: float64
使用loc
、abs
和nsmallest
:
series.loc[series.abs().nsmallest(4).index]
3 -0.25
4 0.25
2 -0.50
5 0.50
dtype: float64
使用Series.abs
和Series.argsort
作为位置,过滤n
,如果性能很重要,则按Series.iloc
选择:
n = 4
series = series.iloc[series.abs().argsort()[:n]]
print (series)
3 -0.25
4 0.25
2 -0.50
5 0.50
dtype: float64
如果需要,最后一个默认索引:
n = 4
series = series.iloc[series.abs().argsort()[:n]].reset_index(drop=True)
print (series)
0 -0.25
1 0.25
2 -0.50
3 0.50
dtype: float64
性能:
series = pd.Series([-1.0,-0.75,-0.5,-0.25,0.25,0.5,0.75,1.0] * 10000)
n = 4000
series = series.iloc[series.abs().argsort()[:n]]
print (series)
In [114]: %timeit series.iloc[series.abs().argsort()[:n]]
794 µs ± 19.4 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
In [115]: %timeit series.loc[series.abs().nsmallest(n).index]
2.09 ms ± 34.7 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)