All - I'm having an issue with trying to plot a model derived from nls() onto a simple plot. I have included a sample data set and the code that I've been using.
year month day date location mileage cost gallon cpg mpg x 2009 1 4 1/4/2009 BZN 124585 19.39 14.37 1.349339 10.71677 2009-01-04 2009 1 15 1/15/2009 BZN 124888 23.2 16.12 1.439206 18.79653 2009-01-15 2009 1 27 1/27/2009 BZN 125133 21.51 14.35 1.498955 17.07317 2009-01-27 2009 2 16 2/16/2009 BZN 125429 27.96 15.54 1.799228 19.04762 2009-02-16 2009 2 27 2/27/2009 BZN 125702 26.82 14.27 1.879467 19.13104 2009-02-27 2009 3 19 3/19/2009 BZN 125941 24.38 12.91 1.888459 18.51278 2009-03-19 2009 4 9 4/9/2009 BZN 126260 32.59 16.30 1.999387 19.57055 2009-04-09 2009 4 28 4/28/2009 BZN 126587 34.58 16.79 2.059559 19.47588 2009-04-28 2009 5 17 5/17/2009 BZN 126925 35.78 16.57 2.159324 20.39831 2009-05-17 2009 5 27 5/27/2009 BZN 127240 35.57 15.01 2.369753 20.98601 2009-05-27 2009 6 7 6/7/2009 BZN 127590 40.99 16.60 2.469277 21.08434 2009-06-07 2009 6 21 6/21/2009 BZN 127910 41.52 15.64 2.654731 20.46036 2009-06-21 2009 7 21 7/21/2009 BZN 128264 43.37 16.67 2.601680 21.23575 2009-07-21 2009 8 11 8/11/2009 BZN 128618 42.68 16.42 2.599269 21.55907 2009-08-11 2009 8 27 8/27/2009 BZN 128947 43.12 16.60 2.597590 19.81928 2009-08-27 2009 9 21 9/21/2009 BZN 129255 40.44 15.56 2.598972 19.79434 2009-09-21 2009 10 1 10/1/2009 BZN 129541 38.55 14.83 2.599461 19.28523 2009-10-01 2009 10 11 10/11/2009 BZN 129806 36.65 14.10 2.599291 18.79433 2009-10-11 2009 10 22 10/22/2009 BZN 130027 30.18 11.61 2.599483 19.03531 2009-10-22 2009 11 9 11/9/2009 BZN 130358 43.19 16.62 2.598676 19.91576 2009-11-09 2009 11 22 11/22/2009 BZN 130631 39.23 15.09 2.599735 18.09145 2009-11-22 2009 12 5 12/5/2009 BZN 130950 44.43 17.09 2.599766 18.66589 2009-12-05 2009 12 30 12/30/2009 BZN 131239 42.14 16.70 2.523353 17.30539 2009-12-30 After converting my dates into R-usable dates: #convert my dates to R-usable dates x <- strptime(date, format="%m/%d/%Y") x mileage <- cbind(mileage, x) I plot the data and model mpg as a function of date. In the nls() statement, I convert x back to a numeric value so that I can conduct the regression: plot(mpg~x, data=mileage[year==2009,], ylab="Miles per gallon", xlab="2009", yaxs="i", ylim=c(10,30)) nls.2009 <- nls(mpg~(alpha*(as.numeric(x)^2))+(bravo*as.numeric(x))+(charlie), data=mileage[year==2009,], start=list(alpha=-2e-14, bravo=5e-5, charlie=-31407), trace=T, na.action=na.omit, nls.control(minFactor=0.000000000000000000001)) plot(mpg~x, data=mileage[year==2009,]) modb=seq(min(as.numeric(x)), max(as.numeric(x)), by=10000) lines(modb, predict(nls.2009, lines(as.numeric(x)=modb))) Unfortunately, when I run the final line of this code, I get the following: Error: unexpected '=' in " lines(modb, predict(nls.2009, lines(as.numeric(x)=" In other similar analyses, I've been able to plot an nls() model using this exact code--altered of course according to information--but here I'm at a loss. I'm certain it has something to do with the lines(...as.numeric(x)) value I'm trying to plot, but I can't figure out what I'm doing wrong. The model is fine, but it's the plotting of the model that escapes me. I'm running R version 2.12.1 on a Windows 7 machine. Thanks for your help - Steven H. Ranney http://stevenranney.blogspost.com http://www.steven-ranney.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.