On Fri, 04 Oct 2024 11:16:45 -0700 Jeff Newmiller via R-help <r-help@r-project.org> wrote:
> Even if this is not a homework question, it smells like one. If you > read the Posting Guide it warns you that homework is off-topic, so > when you impose an arbitrary constraint like "must use specific > unrelated function" we feel like you are either cheating or wasting > our time, and it is up to you to explain why we should follow you > down this rabbit hole, keeping in mind that statistics theory per-se > is also off-topic here. You have yet to explain why you want to do > this the hard way. Well put, Jeff. cheers, Rolf > On October 4, 2024 2:13:26 AM PDT, Steven Yen <sye...@gmail.com> > wrote: > >Pardon me!!! > > > >What makes you think this is a homework question? You are not > >obligated to respond if the question is not intelligent enough for > >you. > > > >I did the following: two ways to calculate a covariance matrix but > >wonder how I might replicate the results with "apply". I am not too > >comfortable with the online do of apply. > > > >> set.seed(122345671) > n<-3 > x<-rnorm(n); x [1] 0.92098449 > >> 0.80940115 > >0.60374785 > cov1<-outer(x-mean(x),x-mean(x))/(n-1); cov1 [,1] [,2] > >[,3] [1,] 0.0102159207 0.00224105983 -0.0124569805 [2,] 0.0022410598 > >0.00049161983 -0.0027326797 [3,] -0.0124569805 -0.00273267965 > >0.0151896601 > cov2<-(x-mean(x))%*%t((x-mean(x)))/(n-1); cov2 [,1] > >[,2] [,3] [1,] 0.0102159207 0.00224105983 -0.0124569805 [2,] > >0.0022410598 0.00049161983 -0.0027326797 [3,] -0.0124569805 > >-0.00273267965 0.0151896601 > > > > >On 10/4/2024 4:57 PM, Uwe Ligges wrote: > >> Homework questions are not answered on this list. > >> > >> Best, > >> Uwe Ligges > >> > >> > >> > >> On 04.10.2024 10:32, Steven Yen wrote: > >>> The following line calculates standard deviations of a column > >>> vector: > >>> > >>> se<-apply(dd,1,sd) > >>> > >>> How can I calculate the covariance matrix using apply? Thanks. ______________________________________________ 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 https://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
