sort()如何在matlab中运行？
纯matlab中的代码：
q是一个数组：
q = -0.2461 2.9531 -15.8867 49.8750 -99.1172 125.8438 -99.1172
49.8750 -15.8867 2.9531 -0.2461
在q = sort(roots(q))之后,我得到了：
q = 0.3525
0.3371 – 0.1564i
0.3371 0.1564i
0.2694 – 0.3547i
0.2694 0.3547i
1.3579 – 1.7880i
1.3579 1.7880i
2.4410 – 1.1324i
2.4410 1.1324i
2.8365
好吧,似乎工作正常！然后在python中,我使用(q与上面相同,它是一个np.array)：
import numpy as np
q = np.sort(np.roots(q))
我得到了：
[ 0.26937874-0.35469815j 0.26937874+0.35469815j 0.33711562-0.15638427j
0.33711562+0.15638427j 0.35254298+0.j 1.35792218-1.78801226j
1.35792218+1.78801226j 2.44104520-1.13237431j 2.44104520+1.13237431j
2.83653354+0.j ]
嗯……这两个结果看起来不同,因为它们排序不同,所以原因是什么？我做错了什么？先感谢您！
我的答案：
def sortComplex(complexList):
complexList.sort(key=abs)
# then sort by the angles,swap those in descending orders
return complexList
If
Ahas complex entriesrands,
sortorders them according to the
following rule:rappears beforesin
sort(A)if either of the following
hold:
abs(r) < abs(s)abs(r) = abs(s)andangle(r) < angle(s)
换句话说,首先基于这些条目的absolute value(即复数量级)对具有复杂条目的数组进行排序,并且基于它们的phase angles对具有相同绝对值的任何条目进行排序.
Python(即numpy)以不同的方式命令.从the documentation Amro linked to in his comment开始：
The sort order for complex numbers is
lexicographic. If both the real and
imaginary parts are non-nan then the
order is determined by the real parts
except when they are equal,in which
case the order is determined by the
imaginary parts.
换句话说,具有复杂条目的数组首先基于条目的实际组件进行排序,并且具有相等实际组件的任何条目基于其虚构组件进行排序.
编辑：
如果要在MATLAB中重现numpy行为,可以使用函数SORTROWS基于数组条目的real和imaginary组件创建排序索引,然后将该排序索引应用于复杂数组值：
>> r = roots(q); %# Compute your roots
>> [junk,index] = sortrows([real(r) imag(r)],[1 2]); %# Sort based on real,%# then imaginary parts
>> r = r(index) %# Apply the sort index to r
r =
0.2694 - 0.3547i
0.2694 + 0.3547i
0.3369 - 0.1564i
0.3369 + 0.1564i
0.3528
1.3579 - 1.7879i
1.3579 + 1.7879i
2.4419 - 1.1332i
2.4419 + 1.1332i
2.8344