先求Ct-t的關系
y=dsolve('Dy-k*(24.8-y)^2=0')
y?=
124/5
124/5?-?1/(25*(C1+?(k*t)/25))再用matlab擬合參數k和C1
t=[0,1,6,12,18,24,30,36,42,48,54,60,72]';
Ct=[24.8?23.86667?23.27333?21.67333?18.48667?16.20667?13.93333...
7.70667?5.98667?4.40667?1.59333?0.66667?0]';
ft_?=?fittype('124/5?-?1/(25*(C1?+?(k*t)/25))',...
'dependent',{'Ct'},'independent',{'t'},...
'coefficients',{'k','C1'});
st=[-0.001?0.4]
[curve,?goodness]=?fit(t,Ct,ft_,'Startpoint',st)
figure,plot(t,Ct,'*'),hold?on,
plot(curve,'predobs',0.99);?
st?=
-0.00100.4000
curve?=?
General?model:curve(t)?=?124/5?-?1/(25*(C1?+?(k*t)/25))
Coefficients?(with?95%?confidence?bounds):k?=-0.001356?(-0.002203,?-0.0005092)
C1?=0.005256?(0.003034,?0.007479)
goodness?=?
sse:?348.0195
rsquare:?0.6773
dfe:?11
adjrsquare:?0.6480
rmse:?5.6248