Running examples in ‘quantchem-Ex.R’ failed
The error most likely occurred in:

> base::assign(".ptime", proc.time(), pos = "CheckExEnv")
> ### Name: AIC.cal
> ### Title: Akaike's An Information Criterion for calibration models
> ### Aliases: AIC.cal
> ### Keywords: models
> 
> ### ** Examples
> 
> data(ibuprofen)
> attach(ibuprofen)
> fit = lmcal(conc,area)
Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

Warning in predict.lm(res$models[[i]], interval = "prediction", level = 0.95,  :
  Assuming constant prediction variance even though model fit is weighted

> AIC(fit)
Error in UseMethod("logLik") : 
  no applicable method for 'logLik' applied to an object of class "c('lmcal', 'cal')"
Calls: AIC -> AIC.default -> ll
Execution halted