# Calculate turning angles and step lengths from location data

[This article was first published on

Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

**Quantitative Ecology**, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

anglefun <- function(xx,yy,bearing=TRUE,as.deg=FALSE){ ## calculates the compass bearing of the line between two points ## xx and yy are the differences in x and y coordinates between two points ## Options: ## bearing = FALSE returns +/- pi instead of 0:2*pi ## as.deg = TRUE returns degrees instead of radians c = 1 if (as.deg){ c = 180/pi } b<-sign(xx) b[b==0]<-1 #corrects for the fact that sign(0) == 0 tempangle = b*(yy<0)*pi+atan(xx/yy) if(bearing){ #return a compass bearing 0 to 2pi #if bearing==FALSE then a heading (+/- pi) is returned tempangle[tempangle<0]<-tempangle[tempangle<0]+2*pi } return(tempangle*c) } bearing.ta <- function(loc1,loc2,loc3,as.deg=FALSE){ ## calculates the bearing and length of the two lines ## formed by three points ## the turning angle from the first bearing to the ## second bearing is also calculated ## locations are assumed to be in (X,Y) format. ## Options: ## as.deg = TRUE returns degrees instead of radians if (length(loc1) != 2 | length(loc2) != 2 | length(loc3) !=2){ print("Locations must consist of either three vectors, length == 2, or three two-column dataframes") return(NaN) } c = 1 if (as.deg){ c = 180/pi } locdiff1<-loc2-loc1 locdiff2<-loc3-loc2 bearing1<-anglefun(locdiff1[1],locdiff1[2],bearing=F) bearing2<-anglefun(locdiff2[1],locdiff2[2],bearing=F) if(is.data.frame(locdiff1)){ dist1<-sqrt(rowSums(locdiff1^2)) dist2<-sqrt(rowSums(locdiff2^2)) }else{ dist1<-sqrt(sum(locdiff1^2)) dist2<-sqrt(sum(locdiff2^2)) } ta=(bearing2-bearing1) ta[ta < -pi] = ta[ta < -pi] + 2*pi ta[ta > pi] = ta[ta > pi] - 2*pi return(list(bearing1=unlist(bearing1*c),bearing2=unlist(bearing2*c), ta=unlist(ta*c),dist1=unlist(dist1),dist2=unlist(dist2))) }

var vglnk = {key: '949efb41171ac6ec1bf7f206d57e90b8'}; (function(d, t) { var s = d.createElement(t); s.type = 'text/javascript'; s.async = true; // s.defer = true; // s.src = '//cdn.viglink.com/api/vglnk.js'; s.src = 'https://www.r-bloggers.com/wp-content/uploads/2020/08/vglnk.js'; var r = d.getElementsByTagName(t)[0]; r.parentNode.insertBefore(s, r); }(document, 'script'));

To

**leave a comment**for the author, please follow the link and comment on their blog:**Quantitative Ecology**.R-bloggers.com offers

**daily e-mail updates**about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.

Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.