This is just (or should be) just a simple example of what I would like to extend to further regression - which is why I was looking for a resource on the grammar.
If I try: lm(ypts ~ exp(xpts)), I only get an intercept and one coefficient. And for the coefficient, I am not sure where that should go? (ie is that A or r in the formula y=A*exp(r*x) ) 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. Thanks! Dieter Menne wrote: > > Brigid Mooney <bkmooney <at> gmail.com> writes: > >> I am doing some basic regression analysis, and am getting a bit >> confused on how to enter non-polynomial formulas to be used. > .. >> But am confused on what the formula should be for trying to find a fit >> to y = A*exp(r*x). > > If this example is just a placeholder for "more complex than poly", > you should check function nls which works for non-linear functions. > > However, if you really want to solve this problem only, doing a > log on you data and fitting a log of the above function with lm() > is the easiest way out. Results can be a bit different from the > nonlinear case depending on noise, because in one case weight > are log-weighted, in the other linearly. > > Dieter > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > > -- View this message in context: http://www.nabble.com/formula-formatting-grammar-for-regression-tp22249014p22251094.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.