Hello I have a vector:
set.seed(123) > n<-3 > x<-rnorm(n); x [1] -0.56047565 -0.23017749 1.55870831 I like to create a matrix with elements containing variances and covariances of x. That is var(x[1]) cov(x[1],x[2]) cov(x[1],x[3]) cov(x[2],x[1]) var(x[2]) cov(x[2],x[3]) cov(x[3],x[1]) cov(x[3],x[2]) var(x[3]) And I like to do it with "apply". Thanks. On 10/4/2024 6:35 PM, Rui Barradas wrote: > Hello, > > If you have a numeric matrix or data.frame, try something like > > cov(mtcars) > > Hope this helps, > > Rui Barradas > > > Às 10:15 de 04/10/2024, Steven Yen escreveu: >> On 10/4/2024 5:13 PM, Steven Yen 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 documentation 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. >> [[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 >> https://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 https://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
