我如何使用scipy.optimize中的leastsq函数将一条直线和二次曲线拟合到下面的数据集中?我知道如何使用polyfit来完成,但我需要使用leastsq函数。
以下是x和y数据集:
x: 1.0,2.5,3.5,4.0,1.1,1.8,2.2,3.7
y: 6.008,15.722,27.130,33.772,5.257,9.549,11.098,28.828
有人能帮我吗?
我如何使用scipy.optimize中的leastsq函数将一条直线和二次曲线拟合到下面的数据集中?我知道如何使用polyfit来完成,但我需要使用leastsq函数。
以下是x和y数据集:
x: 1.0,2.5,3.5,4.0,1.1,1.8,2.2,3.7
y: 6.008,15.722,27.130,33.772,5.257,9.549,11.098,28.828
有人能帮我吗?
leastsq() 方法通过寻找最小化误差函数(yExperimental和yFit之间的差异)的一组参数来进行优化。我使用元组传递参数以及用于线性和二次拟合的Lambda函数。
leastsq()从第一个猜测值(初始参数元组)开始尝试最小化误差函数。如果leastsq()成功,它将返回最适合数据的参数列表。(我打印出来查看)。希望这样可以奏效。 最好的问候
from scipy.optimize import leastsq
import numpy as np
import matplotlib.pyplot as plt
def main():
# data provided
x=np.array([1.0,2.5,3.5,4.0,1.1,1.8,2.2,3.7])
y=np.array([6.008,15.722,27.130,33.772,5.257,9.549,11.098,28.828])
# here, create lambda functions for Line, Quadratic fit
# tpl is a tuple that contains the parameters of the fit
funcLine=lambda tpl,x : tpl[0]*x+tpl[1]
funcQuad=lambda tpl,x : tpl[0]*x**2+tpl[1]*x+tpl[2]
# func is going to be a placeholder for funcLine,funcQuad or whatever
# function we would like to fit
func=funcLine
# ErrorFunc is the diference between the func and the y "experimental" data
ErrorFunc=lambda tpl,x,y: func(tpl,x)-y
#tplInitial contains the "first guess" of the parameters
tplInitial1=(1.0,2.0)
# leastsq finds the set of parameters in the tuple tpl that minimizes
# ErrorFunc=yfit-yExperimental
tplFinal1,success=leastsq(ErrorFunc,tplInitial1[:],args=(x,y))
print " linear fit ",tplFinal1
xx1=np.linspace(x.min(),x.max(),50)
yy1=func(tplFinal1,xx1)
#------------------------------------------------
# now the quadratic fit
#-------------------------------------------------
func=funcQuad
tplInitial2=(1.0,2.0,3.0)
tplFinal2,success=leastsq(ErrorFunc,tplInitial2[:],args=(x,y))
print "quadratic fit" ,tplFinal2
xx2=xx1
yy2=func(tplFinal2,xx2)
plt.plot(xx1,yy1,'r-',x,y,'bo',xx2,yy2,'g-')
plt.show()
if __name__=="__main__":
main()
from scipy.optimize import leastsq
import scipy as sc
import numpy as np
import matplotlib.pyplot as plt
fig, ax = plt.subplots ()
# data
x=np.array([1.0,2.5,3.5,4.0,1.1,1.8,2.2,3.7])
y=np.array([6.008,15.722,27.130,33.772,5.257,9.549,11.098,28.828])
# modeling functions
def funcLine(x, a,b):
return a*x+b
def funcQuad(x, a, b, c):
return a*x**2+b*x+c
# optimize constants for the linear function
constantsLine, _ = sc.optimize.curve_fit (funcLine, x, y)
X=np.linspace(x.min(),x.max(),50)
Y1=funcLine(X, *constantsLine)
# optimize constants for the quadratic function
constantsQuad, _ = sc.optimize.curve_fit (funcQuad, x, y)
Y2=funcQuad(X,*constantsQuad)
plt.plot(X,Y1,'r-',label='linear approximation')
plt.plot(x,y,'bo',label='data points')
plt.plot(X,Y2,'g-', label='quadratic approximation')
matplotlib.pylab.legend ()
ax.set_title("Nonlinear Least Square Problems", fontsize=18)
plt.show()
import random
from scipy.optimize import least_squares
a, b = random.randint(1, 1000), random.randint(1, 1000)
print("Expect", [a, b])
def f(args):
x, y = args
return (x-a)**2 + (y-b)**2
x0 = [-1, -3]
result = least_squares(fun=f, x0=x0)
print(result.x)
leastsq
的不错的教程,你可以尝试按照其中的步骤进行操作,如果遇到困难,请回来编辑这个问题并解释你尝试了哪些方法以及在哪里感到困惑。 - askewchan