formula formatting/grammar for regression

BKMooney <bkmooney <at> gmail.com> writes:

Also, when I tried to use nls, I get an error:  
nls(ypts ~ exp(xpts))
Error in getInitial.default(func, data, mCall = as.list(match.call(func,  : 
  no 'getInitial' method found for "function" objects

If someone could please point out what I am doing wrong, or point me to a
good resource on this, I would greatly appreciate it.  

Read the documents on nls. There is not a simple example of the form 
you used on that page, all have a start value, or a special function
to supply the initial values. For all non-linear fitting, you must 
supply reasonably good starting values, for example from a linear 
fit on the log-transformed data.

Dieter