?dist from the help
dist {stats} R Documentation Distance Matrix Computation Description This function computes and returns the distance matrix computed by using the specified distance measure to compute the distances between the rows of a data matrix. Is this what you want? Computing on a matrix whose rows are your x, y, and z values? On Aug 20, 2014, at 1:12 PM, Patzelt, Edward <patz...@g.harvard.edu> wrote: > R Community - > > I am attempting to write a function that will calculate the distance > between points in 3 dimensional space for unique regions (e.g. localized > brain regions such as the frontal lobe). > > For example I'm looking to compare each point in region 45 to every other > region in 45 to establish if they are a distance of 8 or more apart. I can > do this linearly comparing each distance to the previous but this is not > comparing all points. > > structure(list(Cluster.Index = c(46L, 46L, 46L, 46L, 46L, 45L, > 45L, 45L, 45L, 45L, 44L, 44L, 44L, 44L, 44L, 43L, 43L, 43L, 43L, > 43L), Value = c(8.21, 7.96, 7.85, 7.83, 7.8, 5.38, 4.56, 4.5, > 4, 3.99, 5.42, 4.82, 4.21, 4.18, 3.91, 4.79, 4.27, 3.24, 3.06, > 3.04), x = c(33L, 38L, 37L, 36L, 38L, 47L, 42L, 43L, 44L, 42L, > 50L, 41L, 39L, 41L, 44L, 46L, 45L, 45L, 41L, 46L), y = c(15L, > 12L, 12L, 13L, 13L, 91L, 84L, 84L, 95L, 96L, 69L, 70L, 65L, 65L, > 59L, 41L, 40L, 46L, 44L, 47L), z = c(41L, 38L, 41L, 39L, 33L, > 39L, 40L, 42L, 44L, 45L, 34L, 36L, 30L, 35L, 39L, 53L, 47L, 61L, > 52L, 57L), X = c(NA, 6.557438524302, 3.16227766016838, 2.44948974278318, > 6.32455532033676, 78.7464284904401, 8.66025403784439, 2.23606797749979, > 11.2249721603218, 2.44948974278318, 30.2324329156619, 9.2736184954957, > 8.06225774829855, 5.3851648071345, 7.81024967590665, 22.8910462845192, > 6.16441400296898, 15.2315462117278, 10.0498756211209, 7.68114574786861 > )), .Names = c("Cluster.Index", "Value", "x", "y", "z", "X"), row.names = > c(NA, > 20L), class = "data.frame") > > mainDat <- data.frame() > for(i in 2:nrow(dat)){ > tempDist <- (sqrt((dat$x[i] - dat$x[i-1])^2 + (dat$y[i] - dat$y[i-1])^2 + > (dat$z[i] - dat$z[i-1])^2)) > dat$X[i] <- c(tempDist) > if(dat$Cluster.Index[i] != dat$Cluster.Index[i-1]){ > mainDat <- rbind(mainDat, dat[i,]) > } > if((dat$Cluster.Index[i] == dat$Cluster.Index[i-1])) { > if(tempDist > 8){ > mainDat <- rbind(mainDat, dat[i,]) > } > } > } > > > > > -- > > *Edward H Patzelt | Clinical Science PhD StudentPsychology | Harvard > University * > > [[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. Don McKenzie Research Ecologist Pacific Wildland Fire Sciences Lab US Forest Service Affiliate Professor School of Environmental and Forest Sciences University of Washington d...@uw.edu ______________________________________________ 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.