[英]Numerical solving of overdetermined, nonlinear equation system in Python
這是我的問題的一個最小示例-使用scipy.optimize.leastsq解決
from scipy.optimize import leastsq
from numpy import array, exp, sin, cos
def MatrixFun(x, *par):
a, b, c, d = par
m11 = a*sin(x[0])+b*cos(x[1])
m12 = c*cos(x[0])*sin(x[1])
m21 = c*sin(x[0])/cos(x[1])
m22 = d*exp(x[0]*x[1])
M = array([[m11, m12], [m21, m22]])
return M
def Residualvector(x, parameters):
MatrixAim = MatrixFun([-1 , 1], *parameters)
return (MatrixFun(x, *parameters)-MatrixAim).flatten()
parameters = [1, 2, 3, 4]
start = [0, 0]
print(leastsq(Residualvector, start, args=parameters))
問題:
- 需要一個良好的起點
- 無法在我的實際系統中收斂到所需的值
- 我需要x的約束
這是示例問題的我的蠻力解決方案
from numpy import ones, array, arange, exp, sin, cos, sum, abs, argmin
from itertools import product as iterprod
def MatrixFun(x, *par):
a, b, c, d = par
m11 = a*sin(x[0])+b*cos(x[1])
m12 = c*cos(x[0])*sin(x[1])
m21 = c*sin(x[0])/cos(x[1])
m22 = d*exp(x[0]*x[1])
M = array([[m11, m12], [m21, m22]])
return M
def ResidualMatrix(x, parameters):
MatrixAim = MatrixFun([-1 , 1], *parameters)
return MatrixFun(x, *parameters)-MatrixAim
def MyBruteMatrixMinimizer(ResidualMatrix, ranges, args=()):
pathongrid = list(iterprod(*ranges))
pathlength = len(pathongrid)
MatSum = ones(pathlength)
for i in range(pathlength):
MatSum[i] = sum(abs(ResidualMatrix(pathongrid[i], args)))
pathgoal = pathongrid[argmin(MatSum)]
return pathgoal
parameters = [1, 2, 3, 4]
ranges = [arange(-2,0,1e-2), arange(0,2,1e-2)]
print(MyBruteMatrixMinimizer(ResidualMatrix, ranges, args=parameters))
問題:
- 慢
- 穩定性不清楚
我寧願使用scipy.optimize.brute或scipy.optimize.basinhopping兩者都導致錯誤TypeError: fsolve: there is a mismatch between the input and output shape of the 'func' argument 'F'
。 這很明顯,因為我的矩陣具有比變量更多的方程(超定)。
到目前為止,我唯一的想法是總結盡可能多的方程式的絕對值以減小輸出形狀的大小-但我對此絕對不滿意。
對於替代或改進的解決方案或任何其他建議,我將不勝感激。
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