Thank you for you help Dr. Winsemius. The problem seems to stem from the fact that I have used the incorrect name in the prediction dataframe. The following code seems to work correctly. Thank you again, Michael
wt.data <- data.frame(code = factor(LETTERS[1:24]), area = c(60865,480,656792,92298,1200,1490,8202,4000,220,245,4000,390,325, 16,162911,20235,68800,3389,7,696,4050,1498,1214,99460), species = c(673,650,1353,1026,549,536,782,734,516,580,673,560,641,443,1105, 871,789,575,216,407,942,655,582,1018)) wt.data$logA <- log10(wt.data$area) wt.data$logS <- log10(wt.data$species) wt.mod <- lm(logS~logA, data = wt.data) with(wt.data,plot(logA,logS, ylim = c(2.0,3.5),xlim = c(0,6))) pred.frame <- data.frame(logA = seq(0,6, length.out = 24)) pp <- predict(wt.mod, int = "p", newdata=pred.frame) matlines(pred.frame$logA,pp, lty=c(1,2,2),col="red") Michael Denslow Graduate Student I.W. Carpenter Jr. Herbarium [BOON] Department of Biology Appalachian State University Boone, North Carolina U.S.A. -- AND -- Communications Manager Southeast Regional Network of Expertise and Collections sernec.org > >> > >> # I am not sure how to get the lines to draw > correctly here > >> matlines(pred.frame$a,pp, > lty=c(1,2,2),col="black") > >> > > The x values are your sequence whereas the y values > are in the sequence from the original data. They are not > correctly associated with each other. > > > > Try: > > pp <- predict(lm(wt.data$logS~wt.data$logA), int = > "p", newdata= data.frame(logA=seq(0,6, length.out > = 24)) ) > > plot(pp) > > > At this point I should not have accepted your starting > point. A better starting point would be to use the wt.mod > model: > > pp <- predict(wt.mod, int = "p", newdata= > list(logA=seq(0,6, length.out = 24)) ) > > # Followed by: > > plot( seq(0,6, length.out = 24), pp[ ,"fit"] ) > lines(seq(0,6, length.out = 24), pp[ ,"lwr"], > lty=2) > lines(seq(0,6, length.out = 24), pp[ ,"upr"], > lty=2) > > > > --david winsemius > > > > ______________________________________________ > > 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. > > David Winsemius, MD > Heritage Laboratories > West Hartford, CT ______________________________________________ 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.