The argument k should be a scalar, not a vector. So, for example, this works:
knn.cv(train=predictors.training, cl=classes.training, k=3, prob=TRUE) Jean On Tue, Oct 13, 2015 at 3:59 AM, Neverstop <nevers...@hotmail.it> wrote: > Hi, I'm trying to perform a cross validation to choose the optimal k in the > k-nearest-neighbors algorithm for classification. I'm using the knn > <http://stat.ethz.ch/R-manual/R-devel/library/class/html/knn.html> > function of the package class. Reading the R documentation, I've found out > that there's already a function to perform cross validation: knn.cv > <http://stat.ethz.ch/R-manual/R-devel/library/class/html/knn.cv.html> . > The > problem is that I don't understand how I should use it. > > data(iris) > head(iris) > > predictors.training=iris[c(1:25,51:75,101:125),c("Sepal.Length","Sepal.Width","Petal.Length","Petal.Width")] > > predictors.test=iris[c(26:50,76:100,126:150),c("Sepal.Length","Sepal.Width","Petal.Length","Petal.Width")] > classes.training=iris[c(1:25,51:75,101:125),"Species"] > library(class) > knn.cv(train=predictors.training, cl=classes.training, k=c(1,3,5,7), > prob=TRUE) > > Warning messages: > 1: In if (ntr - 1 < k) { : > the condition has length > 1 and only the first element will be used > 2: In if (k < 1) stop(gettextf("k = %d must be at least 1", k), domain = > NA) > : > the condition has length > 1 and only the first element will be used > > Thank you. > > > > > > -- > View this message in context: > http://r.789695.n4.nabble.com/k-nearest-neighbour-classification-tp4713523.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.