Following up on Rolf's post: 1) cumulative summation (cumsum) maybe? 2) In fact, you should probably **not** fit the non-summation version as you have stated. See ?poly.
I would guess that context is important here. Based on (my interpretation) of the rather strange nature of your request, I suspect that you shouldn't be trying to do what you're doing **at all**; but that's just a guess, of course. -- Bert On Fri, May 18, 2012 at 1:56 PM, Rolf Turner <rolf.tur...@xtra.co.nz> wrote: > On 19/05/12 05:44, Robbie Edwards wrote: >> >> Hi all, >> >> I'm trying to model some data where the y is defined by >> >> y = summation[1 to 50] B1 * x + B2 * x^2 + B3 * x^3 >> >> Hopefully that reads clearly for email. >> >> Anyway, if it wasn't for the summation, I know I would do it like this >> >> lm(y ~ x + x2 + x3) >> >> Where x2 and x3 are x^2 and x^3. >> >> However, since each value of x is related to the previous values of x, I >> don't know how to do this. Any help is greatly appreciated. > > > If your mail says what it seems to say, then your question makes > no sense. You are in effect trying to fit a linear model to a single > point: > > y = B1*s1 + B2*s2 + B3*3 > > where s1 = sum(x), s2 = sum(x^2) and s3=sum(x^3) > > and you have only a single value of each of s1, s2, s3. > > If you have replicate values of s1, s2, and s3 (i.e. replicate > vectors (x1, ... x50)) --- and of course a corresponding y value > for each replicate --- then just form s1, s2, and s3 as vectors > whose entries correspond to the replicates and then fit > > lm(y ~ s1 + s2 + s3) > > If I have misunderstood what you are asking then please provide > a self-contained reproducible example as the posting guide requests. > > cheers, > > Rolf Turner > > ______________________________________________ > 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. -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ 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.