Message-ID: <8A44B0BE-F0BF-45A7-97A1-F0B0B5AEF693@comcast.net>
Date: 2012-12-16T06:03:22Z
From: David Winsemius
Subject: Picking out certain elements in an matrix
In-Reply-To: <CAH=5_TUaJwHdL7g96N9GpeTFL2RRroL2CBSbWu_4HjMhBa7-XA@mail.gmail.com>
On Dec 15, 2012, at 9:38 PM, Tjun Kiat Teo wrote:
> Suppose I have a matrix of data
>
> A
>
> 1 2 3
> 4 5 6
> 7 8 9
>
>
> And I have a vector of indexes 2,1,3
>
> For row 1 of matrix A I want the 2nd element 2
> For row 2 of matrix A I want the 1st element 4
> For row 3 of matrix A I want the 3rd element 9.
A[ cbind( 1:3, c(2,1,3) ) ]
--
David Winsemius
Alameda, CA, USA