我期待做一个剧烈的优化,我使用SciPy来优化债券现金流的折扣因素(应用程序不太重要,但如果感兴趣)。所以基本上我取多个已知值'P',其中P [i]是C [i]已知常数的函数,而数组X(X [j] = x(t)其中x是时间的函数)。其中C [i]和X = P的积和产品。我希望在X(我的x值数组)中有一个约束条件约束x [j] < x [j-1],即x的单调递减。SciPy最小化与单调减少Xs约束
这里是我的最优化函数的代码片段:
在[400]:
import numpy as np
import pandas as pd
import scipy as s
def MyOptimization(X):
P=np.array([99.,100.,105.,110.]) #just example known "P" array, in reality closer to 40 values
c=np.array([1.25,4.,3.1,2.5]) #Cash flows for each P
t=np.array([[1.2,2.,4.,10.0],[0.5,1.],[2.3,5.,10.5],[1.7]]) #time t of each cash flow, multiple per 'P'
#remember P=X(t)*c[i] and x(t) where x[i+1]<x[i]
tlist=[] #t's will be used as index, so pulling individual values
for i in t:
for j in i:
tlist.append(j)
df=pd.DataFrame(data=X,index=tlist).drop_duplicates().sort() #dataframe to hold t (index) and x, x(t), and P(x,c) where c is known
#print df
sse=0
for i in range(0,len(P)):
pxi = np.sum(df.loc[t[i],0].values*c[i])+100*df.loc[t[i][-1],0]
sse=sse+(pxi-P[i])**2 #want to minimize sum squared errors between calculated P(x,c) and known P
return sse
cons=({'type':'ineq','fun': lambda x: x[1] < x[0]}) #trying to define constraint that x is decreasing with t
opti=s.optimize.minimize(MyOptimization,x0=[0.90,0.89,0.88,0.87,0.86,0.85,0.84,0.83,0.82,0.81],bounds=([0,1],)*10,constraints=cons)
在[401]:
opti
出[401]:
status: 0
success: True
njev: 4
nfev: 69
fun: 5.445290696814009e-15
x: array([ 0.90092322, 0.89092322, 0.88092322, 0.94478062, 0.86301329,
0.92834564, 0.84444848, 0.83444848, 0.96794781, 1.07317073])
message: 'Optimization terminated successfully.'
jac: array([ -7.50609263e-05, -7.50609263e-05, -7.50609263e-05,
-5.92906077e-03, 3.46914830e-04, 9.17475767e-03,
-4.89504256e-04, -4.89504256e-04, -1.61263312e-02,
8.35321580e-03, 0.00000000e+00])
nit: 4
而且很明显看到哪里在结果中x数组不减少。 (尝试添加(0,1)范围很好,但结果失败了,所以这里重点放在这,现在
重要的线,我真的不知道有关的约束是:
cons=({'type':'ineq','fun': lambda x: x[1] < x[0]})
我试过下面的文件,但很明显,没有工作。
任何想法不胜感激。
值是否正确,您想更改顺序?或者这些不是你期待的价值。如果数字是好的,但顺序错误,你可以调用'sorted(my_list,reverse = True)'将它们按递减顺序排列 –
对我来说,好像它们不可能是正确的,因为它们不满足约束x [i]
Vlox
我正在阅读scipy.optimize.minimize的文档,看起来你应该设置你的约束它会传递一个非负数。也许尝试'lambda x:x [0] - x [1]' –