[R] Finding cases in one subset that are closet to another subset

[Chuck Cleland]

On 12/2/2009 3:01 PM, Peter Flom wrote:
> Good afternoon
> 
> Running R2.10.0 on Windows
> 
> I have a data frame that includes (among much else) a factor (In_2006) and a continuous variable (math_3_4).  I would like to find the 2 cases for In_2006 = 0 that are closest to each case where In_2006 = 1.
> 
> My data looks like
> 
>      In_2006 math_3_4
>          0     55.1
>          1     51.6
>          1     18.1
>          1     26.6
>          1     14.1
>          1      9.6
>          1     48.9
>          1     12.9
>          0     63.0
>          0     51.8
> 
> etc. for several hundred rows.
> 
> I would like a new data frame that has all the cases where In_2006 = 1, and those cases of In_2006 that are closest to those cases

Hi Peter:

  How about using one of the various matching packages (MatchIt,
optmatch, Matching)?  For example, something like this:


DF <- data.frame(X = rbinom(200, 1, .1), Y = runif(200))

library(MatchIt)

DF.match <- matchit(X ~ Y, data=DF, method='optimal', ratio=2)

DF[c(rownames(DF.match$match.matrix), c(DF.match$match.matrix)),]


hope this helps,

Chuck

> Thanks in advance
> 
> Peter
> 
> Peter L. Flom, PhD
> Statistical Consultant
> Website: www DOT peterflomconsulting DOT com
> Writing; http://www.associatedcontent.com/user/582880/peter_flom.html
> Twitter:   @peterflom
> 
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-- 
Chuck Cleland, Ph.D.
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