Formula: voltage ~ (time < tzero) * (base1 - base2) + base2 + amp * (exp(-kinit * 
    (time >= tzero) * (time - tzero)) - exp(-kdecay * (time >= 
    tzero) * (time - tzero)))

Parameters:
        Estimate Std. Error  t value Pr(>|t|)    
tzero  1.191e+02  2.494e-02 4774.470   <2e-16 ***
base1  2.475e+01  1.323e+01    1.870   0.0618 .  
base2  1.519e+00  8.463e+00    0.179   0.8576    
amp    4.191e+04  5.068e+01  826.893   <2e-16 ***
kinit  1.188e-01  5.726e-04  207.471   <2e-16 ***
kdecay 8.319e-03  1.314e-05  633.344   <2e-16 ***
---
Signif. codes:  0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1 

Residual standard error: 144.3 on 906 degrees of freedom

Correlation of Parameter Estimates:
       t b1 b2 a kn
base1    1         
base2       1      
amp    .       1   
kinit  ,       , 1 
kdecay      ,  , . 
attr(,"legend")
[1] 0 ` ' 0.3 `.' 0.6 `,' 0.8 `+' 0.9 `*' 0.95 `B' 1