Maybe perp.slope = -1/slope abline(cy - cx*perp.slope, perp.slope)
where cx, cy are x- and y-coordinate of C, resp., and slope the slope you calculated for the line through A and B Am 24.Aug.2010 um 0:04 schrieb CZ: > > Hi, > > I am trying to draw a perpendicular line from a point to two points. > Mathematically I know how to do it, but to program it, I encounter some > problem and hope can get help. Thanks. > > I have points, A, B and C. I calculate the slope and intercept for line > drawn between A and B. > I am trying to check whether I can draw a perpendicular line from C to line > AB and get the x,y value for the point D at the intersection. > > Assume I get the slope of the perpendicular line, I will have my point (D) > using variable x and y which is potentially on line AB. My idea was using > |AC|*|AC| = |AD|*|AD|+ |CD|*|CD|. I don't know what function I may need to > call to calculate the values for point D (uniroot?). > > Thank you. > > > > -- > View this message in context: > http://r.789695.n4.nabble.com/Draw-a-perpendicular-line-tp2335882p2335882.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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.
