R help - Jan 2008 - Efficient way to substract all entries in two vectors from each other

Vectors of what? How is "closest" defined? See e.g. ?dist


Bert Gunter
Genentch Nonclinical Statistics


-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Johannes Graumann
Sent: Monday, January 07, 2008 11:19 AM
To: r-help at stat.math.ethz.ch
Subject: [R] Efficient way to substract all entries in two vectors from
eachother

Hi all,

I'm to inexperienced to come up with the matrix solution elusively appearing
on the horizon for the following problem and would appreciate if you could
give me a nudge ...
I have two vectors a, and b and need to find the closest match for each
value of a in b.
How to do that efficiently?

Thanks, Joh

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Hi all,

I'm to inexperienced to come up with the matrix solution elusively appearing
on the horizon for the following problem and would appreciate if you could
give me a nudge ...
I have two vectors a, and b and need to find the closest match for each
value of a in b.
How to do that efficiently?

Thanks, Joh

Johannes Graumann wrote:
> Hi all,
> 
> I'm to inexperienced to come up with the matrix solution elusively
> appearing on the horizon for the following problem and would appreciate if
> you could give me a nudge ...
> I have two vectors a, and b and need to find the closest match for each
> value of a in b.
> How to do that efficiently?
I am not sure if I understood your problem correctly, 
but maybe this is of help.
However its not memory efficient.
> a <- c(3,10,50,100)
> b <- c(7,8,300)
> b[apply(abs(outer(a,b,"-")),1,which.min)]
[1] 7 8 8 8

In Biobase there is the matchpt function doing this
efficiently.

best wishes,
ido