Annotate a segmented linear regression plot
On Oct 2, 2012, at 3:38 PM, Ben Harrison wrote:
On 28 September 2012 16:38, David Winsemius <dwinsemius at comcast.net> wrote:
?text # should be fairly clear.
Thank you. I was stupid to ask such a trivial question along with a not-so-trivial one. The second part of the question was probably more important: is there a way to obtain the location of segments produced by the segmented package, so that I can annotate them easily?
I guess it depends on what you mean by "the location of segments". It's easy enough to retrun the x-values for the knots:
o$psi[ , "Est."]
I do not see a `predicted.segmented` function, so might need to construct separate lm.predict estimates for values between the pairs of x-values if you meant you wanted the y-values for the knots.
David. > > I have since asked this question of Vito, the package's author. Here > is his response: > > ##### > dear Ben, > here a possible solution, > > o is the segmented fit > > r<-o$rangeZ[,1] > est.psi<-o$psi[,2] > v<-sort(c(r, est.psi)) > xCoord<-rowMeans(cbind(v[-length(v)], v[-1])) > > Z<-o$model[,o$nameUV$Z] > > id<-sapply(xCoord, function(x)which.min(abs(x-Z))) > yCoord<-broken.line(o)[id] > > plot(o, col=2:4, res=T) > text(xCoord, yCoord, labels=formatC(slope(o)[[1]][,1], digits=2), > pos=4, cex=1.3) > > Play with pos, cex and digits to modify the appearance of the labels. > > vito > ##### > >> Please learn to post in plain text. > > I hope this is better. > > Ben. David Winsemius, MD Alameda, CA, USA