第1个回答 推荐于2018-02-27
clc;clear
x=[0.3 0.313824576 0.328286214 0.343414273 0.359239461 0.375793905 0.393111209 0.411226528 0.430176635 0.45]
y=[0.25 0.4375 0.59375 0.78125 0.875 0.9375 0.96875 0.96875 1 1 ]
fx =inline('(1-0.02)-(1-0.25-0.02)*2.^(-(x./a(1)).^a(2))','a','x')%拟合并求y=0.75时x的值
a=nlinfit(x,y,fx,[1 1])
x1=min(x):0.001:max(x);
y1=(1-0.02)-(1-0.25-0.02)*2.^(-(x1./a(1)).^a(2));
f=vpa(subs(fx,'[a(1),a(2)]',[a(1),a(2)])-0.75,6)
x75=solve(f)
plot(x,y,'o',x1,y1)
grid
结果:
fx =
Inline function:
fx(a,x) = (1-0.02)-(1-0.25-0.02)*2.^(-(x./a(1)).^a(2))
a =
0.33229 16.846
f =
.230000-.73*2.^(-.114971e9*x^(4741802551867469/281474976710656))
x75 =
.34251812790298161188357974505310本回答被提问者和网友采纳