[R] does range of values in array include a third value?

[David Winsemius]

On Feb 17, 2011, at 10:36 AM, Maas James Dr (MED) wrote:

>
> I'm using the range command to get the minimum and maximum values of  
> an array as in
>
> x <- range(array_y)
>
> which gives me two values such as
>
> [1] -2 9
>
> I need to be able to test if this range of values includes a third  
> value.  For example I'd like to query
>
> 1) does the range of -2 to 9 include 3, answer TRUE
> 2) does the range of -2 to 9 include -6, answer FALSE?
>
> All values could be negative or positive.  Is there a R function  
> that will test this or do I need to programme it?  I have searched  
> but not found one.

There is a function that handles intervals well, findInterval:

 > findInterval(0, c(-2, 9))
[1] 1
 > findInterval(-3, c(-2, 9))
[1] 0
 > findInterval(10, c(-2, 9))
[1] 2

So:

isxInRange_y <- function(x, y) findInterval(x, range(y)) == 1

If you want to omit NA's which would otherwise poison the effort, you  
need to wrap the y argument in na.omit().

-- 
David.

>
> Thanks
>
> J
>
> ===============================
> Dr. Jim Maas
> University of East Anglia
>
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
West Hartford, CT