[R] How to find best parameter values using deSolve n optim() ?

[mhimanshu]

Hi Thomas,

Thank you so much for your suggestion. 
I tried your code and it is working fine. Now when I change the values of Y
in yobs I am getting so many warnings.

say, 
yobs <- data.frame(
 time = 0:7,
 Y = c(0.00, 3.40, 4.60 ,5.80, 5.80, 6.00, 6.00 ),
 Z = c(0.1, 0.11, 0.119, 0.128, 0.136, 0.145, 0.153, 0.16)
)

So when i fit the model with the same code that you have written, i got the
following warnings:
DLSODA-  Warning..Internal T (=R1) and H (=R2) are                              
      such that in the machine, T + H = T on the next step                      
     (H = step size). Solver will continue anyway.                              
      In above,  R1 =  0.1484502806322D+01   R2 =  0.2264549048113D-16

and I have got so many such warnings.

Can you explain me why this is happening??  and Secondly,  I dont understand
why i am getting parameters values in negatives after fitting?? Can you
please help me out in this... :)

Thanks
Himanshu

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