Let's say your fixed vector is x, and y is the list of vectors that you want to create the squared distance to x with, then:
x<-c(1:5) y<-list() y[[1]]<-sample(c(1:5),5) y[[2]]<-sample(c(1:5),5) y[[3]]<-sample(c(1:5),5) y distances<-lapply(y,function(a,b) crossprod(a-b), b=x) #lapply goes over the list elements of y and executes the function for each of these list elements #the current list element of "y" is plugged in for "a" and "x" is plugged in for "b" and the crossproduct is formed distances<-unlist(distances) HTH, Daniel Wei Wu wrote: > > I am pretty new to R. So this may be an easy question for most of you. > > I would like to calculate the squared distances of a large set (let's say > 20000) of vectors (let's say dimension of 5) to a fixed vector. > > Say I have a data frame MY_VECTORS with 20000 rows and 5 columns, and one > 5x1 vector y. I would like to efficiently calculate the squared > distances between each of the 20000 vectors in MY_VECTORS and y. > > The squared distance between two vectors x and y can be calculated: > distance <- crossprod(x-y) > > Without looping, what is the efficient code to achieve this? > > Thanks. > > ______________________________________________ > 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. > -- View this message in context: http://r.789695.n4.nabble.com/Efficient-way-to-Calculate-the-squared-distances-for-a-set-of-vectors-to-a-fixed-vector-tp3764589p3764616.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.
