As x goes from 200 to 400, y goes from ,004 to .016 so y is quadrupling while x doubles -- quadratic growth. Fitting to a quadratic and plotting shows this to be the case. Note that for y to be quadratic in x it must be linear in the coefficients of x so we can just use lm and don't need nls:
plot(y ~ x) y.lm <- lm(y ~ poly(x, 2)) lines(x, fitted(y.lm)) y.lm On Sun, Jan 11, 2009 at 9:19 PM, Nathan S. Watson-Haigh <nathan.watson-ha...@csiro.au> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > I have the following data: > >> y > [1] 0.000 0.004 0.008 0.016 0.024 0.032 0.044 0.064 0.072 0.088 0.108 0.140 > [13] 0.156 0.180 0.208 0.236 0.264 0.296 0.320 0.360 0.408 0.444 0.472 0.524 > [25] 0.576 >> x > [1] 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 > 1500 > [16] 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 > > I'd like to plot the points and calculate a curved line of best fit. I know I > need to use nls(), but > I'm unsure how to begin....any pointers? > > Cheers, > Nathan > > > - -- > - -------------------------------------------------------- > Dr. Nathan S. Watson-Haigh > OCE Post Doctoral Fellow > CSIRO Livestock Industries > Queensland Bioscience Precinct > St Lucia, QLD 4067 > Australia > > Tel: +61 (0)7 3214 2922 > Fax: +61 (0)7 3214 2900 > Web: http://www.csiro.au/people/Nathan.Watson-Haigh.html > - -------------------------------------------------------- > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.9 (MingW32) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org > > iEYEARECAAYFAklqqJsACgkQ9gTv6QYzVL4gCgCgy4qShoFX/9QWgKsBqHPhLCDS > r+AAnRD3kbkImG3rVaBN6d4BP2cUmqYZ > =yVLj > -----END PGP SIGNATURE----- > > ______________________________________________ > 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. > ______________________________________________ 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.
