If it's a one off, the identify() function might be of help -- if you need something algorithmic it's harder due to floating point stuff and sampling frequencies. Let me know if that's the case.
Michael On Nov 22, 2011, at 3:40 PM, Monica Pisica <pisican...@hotmail.com> wrote: > > > > Hi everyone, > > > > I am trying to get a point of intersection between a > polyline and a straight line ….. and get the x and y coordinates of this > point. > For exemplification consider this: > > > > > > set.seed(123) > > > > k1 <-rnorm(100, mean=1.77, sd=3.33) > > k1 <- sort(k1) > > q1 <- rnorm(100, mean=2.37, sd=0.74) > > q1 <- sort(q1, decreasing = TRUE) > > plot(k1, q1, xlim <- c((min(k1)-5), (max(k1)+5)), > type="l") > > > > ya <- 2 > > xa = -5 > > yb=4 > > xb=12 > > > > lines(c(xa, xb), c(ya, yb), col = 2) > > > > # I want to get the x and y coordinates of the > intersection of the 2 lines …. > > > > m <- (ya-yb)/(xa-xb) > > b <- ya-m*xa > > ln <- loess(q1~k1) > > lines(ln) > > > > It is clear that the x, y will satisfy both linear > equations, y = m*x + b and the ln polyline ….. but while I can visualize the > equation of the straight line – I have problems with the polyline. I will > appreciate > any ideas to solve this problem. I thought it a trivial solution but it seems > I > cannot see it. > Thanks, > Monica > > > > ______________________________________________ > 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. ______________________________________________ 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.
