> Hi > I have measured the UV absorbance (abs) of 10 solutions of a > substance at known concentrations (conc) and have used a > linear model to plot a calibration graph with confidence > limits. I now want to predict the concentration of solutions > with UV absorbance results given in the new.abs data.frame, > however predict.lm only appears to work for new "conc" > variables not new "abs" variables. > > I have search the help files and did find a similar problem > in June 2000, but unfortunately no solution was offered. Any > help and how to use predict.lm with the new "abs" data to > predict "conc" with confidence limits would be appreciated. > > conc<-seq(100, 280, 20) # mg/l > abs<-c(1.064, 1.177, 1.303, 1.414, 1.534, 1.642, 1.744, > 1.852, 1.936, > 2.046) # absorbance units > lm.calibration<-lm(abs ~ conc) > pred.w.plim <- predict(lm.calibration, interval="prediction") > pred.w.clim <- predict(lm.calibration, interval="confidence") > matplot(conc, cbind(pred.w.clim, pred.w.plim[,-1]), > lty=c(1,2,2,3,3), type="l", ylab="abs", xlab= > "conc mg/l") > points(conc, abs, pch=21, col="blue") > > new.abs<-data.frame(abs=c(1.251, 1.324, 1.452)) > > predict(calibration.lm, new.abs) # does not work
lm.calibration predict(lm.calibration, new.abs) Is this the reason for not working? Best, Matthias > > > Thanks > Mike White > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read > the posting guide! http://www.R-project.org/posting-guide.html > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
