Fit

gkokovidis — Wed, 30 May 2012 06:22:35 Z

While the detailed math relationship can be found in the picture,
extracting detailed data pairs is rather difficult.
A digitizing program that generates x-y pairs could be used.
The more data, the better the fit. Fitting the picture with a simple math function,
without using piecewise or splines is not straight forward.
Below is a very rough attempt to do so by estimating x-y pairs.

restart: with(plots):
with(Statistics):
X := Vector([1, 25,50,75,100, 125,200, 300, 400, 500, 600]):
Y := Vector([40e3,8e3, 2000,600,350, 210,200, 180, 170, 150,140]):
eq:=NonlinearFit(a+b*exp(-c*t)+d^(-t), X, Y, t);
logplot(eq,t=0..600,y=1..100000,gridlines=true);

nonlinearfit.mw

Regards,

Georgios Kokovidis

Dräger Medical

Tks,gkokovidis

andy.zhou.nuaa — Thu, 31 May 2012 07:46:29 Z

You answer is very useful to me. Although there is a little dismatch on the condition of vds>300, the precision is enough for my appliction.

tks again for ur help.

MaplePrimes - answers and comments on Question, Can anyone fitting this curve by simple math function

Fit

Tks,gkokovidis