[R] Selecting rows according to a column

[Erik Iverson]

Hello,

Here's an idea: 

ifelse(z$c == "a", z$a, z$b)


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of Gurpal Kalsi
> Sent: Wednesday, October 28, 2009 11:15 AM
> To: r-help at r-project.org
> Subject: [R] Selecting rows according to a column
> 
> Hi,
> 
> With a data such as:
> > z = data.frame(a = 1:5, b=10*a, c = c("a", "a", "b", "b", "b") )
> * a  b  c*
>  *1* 10 *a*
>  *2* 20 *a*
>  3 *30* *b*
>  4 *40* *b*
>  5 *50* *b*
> 
> Can anyone suggest a way to select [1, 2, 30, 40, 50],
> ie. using column "c" to specify which column is selected for each row.
> 
> Many thanks
> 
> G
> 
> 	[[alternative HTML version deleted]]
> 
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