[R] moving distance between two sets of data

[White, William Patrick]

The first method described produces a value other than the desired output every time the Firstset value is positive and the Secondset is negative, such as the second instance when seed is set to 123. The second method described produces a value other than the desired output every time the Firstset is negative and Secondset is positive, such as the first value derived from seed 123.


________________________________________
From: David Winsemius [dwinsemius at comcast.net]
Sent: Sunday, August 19, 2012 3:58 PM
To: White, William Patrick
Cc: r-help at r-project.org
Subject: Re: [R] moving distance between two sets of data

On Aug 19, 2012, at 12:04 PM, White, William Patrick wrote:

> On the surface this seems pretty simple, but I flummoxed. I have two
> sets of numbers they bounce around zero, positive one and negative
> one. They have a relationship between them, where one diverges away
> from the other. I want create a second set of numbers that tracks
> that divergence.
>
> #Lets make some data like mine, kinda
> Firstset <- runif(100, min = -1 , max =1)
> Secondset <- runif(100, min = -1 , max =1)
>
> #So something like:
> Divergence <- abs (Firstset - Secondset)
>
> #but this doesn't work because when Firstset is at .5 and Secondset
> is at  -.25 it returns .25 instead of .75

   abs( .5 - (-.25) ) should NOT return .25 so you need to produce a
better example or point to specifics in the example you offered. If
what you wanting what you are getting, then use set.seed(123) and
refer to specific values.

 > abs( .5 - (-.25) )
[1] 0.75

--
David.

>
> #another possibility is:
>
> Divergence <- abs (Firstset) - abs (Secondset)
>
> #but when Firstset is at .5 and Secondset is at -.5 it returns 0
> instead of 1
>
> #It seems like there is a better way to do this. Any ideas?
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David Winsemius, MD
Alameda, CA, USA