[R] equivalent R functions for Numerical Recipes fitxy and fitexy ?

[Marc Fischer]

Dear Folks,

We need to fit the model y~x  assuming there are random errors in both  
x and y.  Numerical Recipes (Press et al.) have two useful functions,  
fitxy and fitexy, which handle cases of unspecified and specified  
errors respectively.

Are there equivalent functions in base R or a installable package?    
Alternatively, has anyone written a wrapper to provide an interface to  
a library of Numerical Recipes routines constructed for Linux?

Kind regards,

Marc