  
  Hi,

I fitted tree growth data with Chapman-Richards growth function using nls. 

summary(fit.nls) 

Formula: HEIGHT ~ A * (1 - exp(-B * AGE))^C 

Parameters: 

  Estimate Std. Error t value Pr(>|t|)    
A 29.007627  0.270485  107.24  <2e-16 ***
B  0.030813  0.001095  28.13  <2e-16 ***
C  1.849405  0.068659  26.94  <2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 

Residual standard error: 1.879 on 713 degrees of freedom

Algorithm "port", convergence message: relative convergence (4) 

When I try to run the anova() function I get this:

anova(fit.nls)
Error in anova.nls(fit.nls) : anova is only defined for sequences of "nls" objects

Could you tell me what the problem is?

Thanks & Regards,
Guru S 

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