[R] packages masking other objects

[James Smith]

hello all, 

I am trying to use the function getCovariateFormula(nlme) in conjunction with the library lme4. When I load both packages I get the following message and the getCovariateFormula function no longer works:

library(nlme)
library(lme4)

Attaching package 'lme4':


        The following object(s) are masked from package:nlme :

         contr.SAS getCovariateFormula getResponseFormula groupedData lmeControl 

I have tried removing the package after using it, with:
detach(package:lme4)
library(nlme)

but I still get an error message when I try to use getCovariateFormula. The line I use it in, and the error message is below:

rownames(table)<-c((getCovariateFormula(model1)),(getCovariateFormula(model2)),(getCovariateFormula(model3)),(getCovariateFormula(model4)),(getCovariateFormula(model5)),(getCovariateFormula(model6)),(getCovariateFormula(modelnull)))

Error in switch(mode(x), "NULL" = structure(NULL, class = "formula"),  : 
        invalid formula

This line works fine when I run models with different structures that are not in the lme4 package.
Does anyone have any suggestions about this ?
Am I not removing the package completely ?

Any suggestions would be greatly appreciated
Thanks
James Smith