[英]Optimization using scipy
我正在尝试建立一个类似Markowitz问题的有效边界。 我已经写了下面的代码,但出现错误“ ValueError:目标函数必须返回标量”。 我已经用一些值测试了“有趣”,例如,我输入到控制台:
W = np.ones([n])/n # start optimization with equal weights
cov_matrix = returns.cov()
fun = 0.5*np.dot(np.dot(W, cov_matrix), W) # variance of the portfolio
fun
输出为0.00015337622774133828,它是一个标量。 我不知道有什么问题。 任何帮助表示赞赏。
from scipy.optimize import minimize
import pandas as pd
import numpy as np
from openpyxl import load_workbook
wb = load_workbook('path/Assets_3.xlsx') # in this workbook there is data for returns.
# The next lines clean unnecessary first column and first row.
ws = wb.active
df = pd.DataFrame(ws.values)
df1 = df.drop(0,axis=1)
df1 = df1.drop(0)
df1 = df1.astype(float)
rf = 0.05
r_bar = 0.05
returns = df1.copy()
def efficient_frontier(rf, r_bar, returns):
n = len(returns.transpose())
W = np.ones([n])/n # start optimization with equal weights
exp_ret = returns.mean()
cov_matrix = returns.cov()
fun = 0.5*np.dot(np.dot(W, cov_matrix), W) # variance of the portfolio
cons = ({'type': 'eq', 'fun': lambda W: sum(W) - 1. },
{'type': 'ineq', 'fun': lambda W: np.dot(exp_ret,W) - r_bar })
bnds = [(0.,1.) for i in range(n)] # weights between 0..1.
res = minimize(fun, W, (returns, cov_matrix, rf),
method='SLSQP', bounds = bnds, constraints = cons)
return res
x= efficient_frontier(rf,r_bar,returns)
x
1 2 3
1 0.060206 0.005781 0.001117
2 0.006463 -0.007390 0.001133
3 -0.003211 -0.015730 0.001167
4 0.044227 -0.006250 0.001225
5 -0.040571 -0.006910 0.001292
6 -0.007900 -0.006160 0.001208
7 0.068702 0.013836 0.001300
8 0.039286 0.009854 0.001350
9 0.012457 -0.007950 0.001358
10 -0.013758 0.001021 0.001283
11 -0.002616 -0.013600 0.001300
12 0.059004 -0.006090 0.001442
13 0.015566 0.002818 0.001308
14 -0.036454 0.001395 0.001283
15 0.058899 0.011072 0.001325
16 -0.043086 0.017070 0.001308
17 0.023156 -0.003350 0.001392
18 0.063705 0.000301 0.001417
19 0.017628 -0.001960 0.001508
20 -0.014567 -0.006990 0.001525
21 -0.007191 -0.013000 0.001425
22 -0.000815 0.014773 0.001450
23 0.046493 -0.001540 0.001542
24 0.051832 -0.008580 0.001742
25 -0.007151 0.001177 0.001633
26 -0.018196 -0.008680 0.001642
27 -0.013513 -0.008810 0.001675
28 -0.026493 -0.010510 0.001825
29 -0.003249 -0.014750 0.001800
30 0.001222 0.022258 0.001758
这段代码是一团糟,尽管我可以向您展示可以运行的内容,但这并不意味着任何事情。
无论您的任务意味着什么,您都将看到收敛到起点的方法! 这有力地表明有些事情还是非常错误的(可能是基础理论)!
一些补充说明:
df
和returns.cov()
,对于numpy-arrays不存在! 码:
from scipy.optimize import minimize
import numpy as np
import pandas as pd
rf = 0.05
r_bar = 0.05
returns = pd.DataFrame(np.random.randn(30, 3), columns=list('ABC')) # PANDAS DF
cov_matrix = returns.cov().as_matrix() # use PANDAS one last time
# but result = np.array!
returns = returns.as_matrix() # From now on: np-only!
def fun(x, returns, cov_matrix, rf):
return 0.5*np.dot(np.dot(x, cov_matrix), x)
def efficient_frontier(rf, r_bar, returns):
n = len(returns.transpose())
W = np.ones([n])/n # start optimization with equal weights
exp_ret = returns.mean()
cons = ({'type': 'eq', 'fun': lambda x: np.sum(x) - 1. }, # let's use numpy here
{'type': 'ineq', 'fun': lambda x: np.dot(exp_ret, x) - r_bar })
bnds = [(0.,1.) for i in range(n)] # weights between 0..1.
res = minimize(fun, W, (returns, cov_matrix, rf),
method='SLSQP', bounds = bnds, constraints = cons)
return res
x= efficient_frontier(rf,r_bar,returns)
print(x)
输出:
A B C
A 0.813375 -0.001370 0.173901
B -0.001370 1.482756 0.380514
C 0.173901 0.380514 1.285936
fun: 0.2604530793556774
jac: array([ 0.32863522, 0.62063321, 0.61345008])
message: 'Optimization terminated successfully.'
nfev: 35
nit: 7
njev: 3
status: 0
success: True
x: array([ 0.33333333, 0.33333333, 0.33333333])
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