[R] creating matrices from vectors

[Patrick Burns]

I think this approximates what you want:

a1 <- 1:10
a2 <- a1 + 100
a3 <- a1 + 200
a4 <- a1 + 300

arr <- rbind(a1, a2, a3, a4)
dim(arr) <- c(2, 2, 10)
apply(arr, 3, function(x) eigen(x)$values[2])

Patrick Burns
patrick at burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of S Poetry and "A Guide for the Unwilling S User")

James Rudge wrote:
> If I have 4 vectors (a, b, c, and d) each of length 1000, how do I then create 1000 two by two matrices from these vectors, such that:
>  
> myMatrix[i] = matrix(c(a[i],b[i],c[i],d[i]),2)
>  
> Then I'd like to create a single vector containing the largest eigenvalues of each matrix?
>  
> (Sorry I am quite new to R)
> Many thanks,
> James
>  
> _________________________________________________________________
> [[elided Hotmail spam]]
>
> ______________________________________________
> R-help at 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.
>
>
>