ID1  ID2     t               V(t)
1       1       0               6.053078443
2       1       0.3403  5.56937391
3       1       0.4181  5.45484486
4       1       0.4986  5.193124598
5       1       0.7451  4.31386722
6       1       1.0069  3.645422269
7       1       1.5535  3.587710965
8       1       1.8049  3.740362689
9       1       2.4979  3.699837726
10      1       6.4903  2.908485019
11      1       13.5049 1.888179494
12      1       27.5049 1.176091259
13      1       41.5049 1.176091259

The model
(1)  V(t)=V0[1-epi+ epi*exp(-c(t-t0))]
(2)  V(t)=V0{A*exp[-lambda1(t-t0)]+(1-A)*exp[-lambda2(t-t0)]}

in formula (2) lambda1=0.5*{(c+delta)+[(c-delta)^2+4*(1-epi)*c*delta]^0.5}
                  
lambda2=0.5*{(c+delta)-[(c-delta)^2+4*(1-epi)*c*delta]^0.5}
                   A=(epi*c-lambda2)/(lambda1-lambda2)

The regression rule :
for formula (1):(t<=2,that is) first 8 rows are used for non-linear
regression
epi,c,t0,V0 parameters are obtained 
for formula (2):all 13 rows of results are used for non-linear regression 
lambda1,lambda2,A (with these parameters, delta can be calculated from them)

Thanks for help
Ster Lesser

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