[R] counting the number of ones in a vector

[Gavin Simpson]

On Fri, 2010-02-26 at 10:43 -0800, David Reinke wrote:
> The length will remain the same no matter what expression appears in
> the subscript.

No it won't! x == 1 evaluates to logical and when used to *subset* x, it
*will* return the required answer. As observed with this example:

> set.seed(1)
> x <- sample(rep(1:3, times = 20))
> x
 [1] 1 1 1 1 3 2 3 3 3 1 2 3 3 1 2 2 2 1 3 2 2 1 1 2 1 2 1 1 1 1
[31] 3 3 2 3 2 2 2 3 3 3 1 3 3 1 3 2 1 1 2 2 1 1 3 2 2 3 2 2 3 3
> 
> ## compare
> sum(x == 1, na.rm = TRUE)
[1] 20
> length(x)
[1] 60
> length(x[x == 1])
[1] 20

G

>  I suggest this:
> 
> sum(x == 1)
> 
> David Reinke
> 
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> 
> 
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Randall Wrong
> Sent: Friday, February 26, 2010 6:44 AM
> To: r-help at r-project.org
> Subject: [R] counting the number of ones in a vector
> 
>  Dear R users,
> 
> I want to count the number of ones in a vector x.
> 
> That's what I did : length( x[x==1] )
> 
> Is that a good solution ?
> 
> Thank you very much,
> Randall
> 
> 	[[alternative HTML version deleted]]
> 
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> ______________________________________________
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