[R] nls error regarding numerics vs logicals

[Jim Bouldin]

> 1.  The expression you gave us is clearly not the one that produced the 
> error:  it involved "ring.area" and "ba.beg".
> 
> 2.  You don't tell us what x and y are, so we can't reproduce anything.

Sorry, I guess that was unclear.  I changed the response and independent
variable names to y and x respectively, in hopes that would be clearer.
Both are numeric variables.
Jim