Hi Folks, I'm looking to do Confidence bands around LOESS smoothing curve.
If found the older post about using the Standard error to approximate it https://stat.ethz.ch/pipermail/r-help/2008-August/170011.html Also found this one http://www.r-bloggers.com/sab-r-metrics-basics-of-loess-regression/ But they both seem to be approximations of confidence intervals and I was wonder if there was a way to get the CIs? Below is the code I have so far and my data is no the net. Any help would be greatly appreciated. Take Care David ----------------------------- #Load your data. Is located on the web at the address below mydata <- read.csv("http://doylesdartden.com/smoothing.csv";, sep=",") mydata <- read.table("x.csv", header=TRUE, sep=",",) attach(mydata) reg1 <- lm(Y_Axis_Parameter~X_Axis_Parameter) par(cex=1) * * * * #Plots the data but makes nondetects a different color and type based on column D_Y_Axis_Parameter being a 0 for ND and 1 for detect. plot(X_Axis_Parameter, Y_Axis_Parameter, col=ifelse(D_Y_Axis_Parameter, "black", "red"),ylab = "Y_Axis_Parameter", pch=ifelse(D_Y_Axis_Parameter, 19, 17), cex = 0.7) plx<-predict(loess(Y_Axis_Parameter ~ X_Axis_Parameter, data=mydata), se=T) lines(mydata$X_Axis_Parameter,plx$fit+2*plx$s, lty=2) #rough & ready CI lines(mydata$X_Axis_Parameter,plx$fit-2*plx$s, lty=2) # Apply loess smoothing using the default span value of 0.8. You can change the curve by changing the span value. y.loess <- loess(y ~ x, span=0.8, data.frame(x=X_Axis_Parameter, y=Y_Axis_Parameter)) # Compute loess smoothed values for all points along the curve y.predict <- predict(y.loess, data.frame(x=X_Axis_Parameter)) # Plots the curve. lines(X_Axis_Parameter,y.predict) * * #Add Legend to graY_Axis_Parameter. You can change the size of the box by changing cex = 0.75 Large # makes it larger. legend("topleft", c("Smoothing Curve", "Detected", "NonDetect"), col = c(1, "black","red"), cex = 0.75, text.col = "black", lty = c(1 ,-1, -1), pch = c(-1, 19, 17), merge = TRUE, bg = 'gray90') * * #Add title title(main="Locally Weighted Scatterplot Smoothing Curve") # Done [[alternative HTML version deleted]] ______________________________________________ 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.
