# [R] creating matrices from vectors

Patrick Burns pburns at pburns.seanet.com
Sat Nov 15 18:52:59 CET 2008

```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)

Patrick Burns
patrick at burns-stat.com
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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
>
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