> a <- matrix (1:16, 4, 4)
> b <- c (2,3)
>
> which(a[, 1] %in% b)
[1] 2 3
>
> a
[,1] [,2] [,3] [,4]
[1,] 1 5 9 13
[2,] 2 6 10 14 ## <<----
[3,] 3 7 11 15 ## <<----
[4,] 4 8 12 16
>
Bill Venables
CSIRO Laboratories
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-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Waverley
Sent: Monday, 10 March 2008 9:23 AM
To: r-help; r-help@r-project.org
Subject: [R] question about matrix one column values matching a vector
ofvalues
Hi,
I have a matrix
a = matrix (1:16, 4, 4)
b = c (2,3)
I want to find out which rows of a, where a[,1] equals any values of b?
I know that if b is only one value, e.g, b=2, then what I want is
a[a[,1] == 2,]
But what about if it is not one value but a vector of values?
Thanks much in advance.
--
Waverley @ Palo Alto
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
