find closest value in a vector based on another vector values

Bert,

thanks... The values should not repeat themselves if the same a is closest to all b, so probably aruns example extended with a unique command works best?

unique(a[sapply(b,function(x) which.min(abs(x-a)))])

thanks,

Andras

--- On Tue, 6/18/13, Bert Gunter <gunter.berton at gene.com> wrote:

From: Bert Gunter <gunter.berton at gene.com>
Subject: Re: [R] find closest value in a vector based on another vector values
To: "Jorge I Velez" <jorgeivanvelez at gmail.com>
Cc: "Andras Farkas" <motyocska at yahoo.com>, "R mailing list" <r-help at r-project.org>
Date: Tuesday, June 18, 2013, 10:07 AM
Jorge: No.

a <-c(1,5,8,15,32,33.5,69)
b <-c(8.5,33)
a[findInterval(b, a)]

[1]  8 32  ##should be
8   33.5

I believe it has to be done explicitly by finding all the
differences
and choosing those n with minimum values, depending on what
n you
want.

Note that the problem is incompletely specified. What if the
same
value of a is closest to several values of b? -- do you want
all the
values you choose to be different or not, in which case they
may not
be minimum?

a <- c(1, 8, 9)
b <- c(2,3)

Then what are the 2 closest values of a to b?

-- Bert

On Tue, Jun 18, 2013 at 5:43 AM, Jorge I Velez <jorgeivanvelez at gmail.com>
wrote:

Dear Andras,

Try

a[findInterval(b, a)]

[1]  8 32

HTH,
Jorge.-


On Tue, Jun 18, 2013 at 10:34 PM, Andras Farkas <motyocska at yahoo.com>

wrote:

Dear All,

would you please provide your thoughts on the

following:

let us say I have:

a <-c(1,5,8,15,32,69)
b <-c(8.5,33)

and I would like to extract from "a" the two values

that are closest to

the values in "b", where the length of this vectors

may change but b will

allways be shorter than "a". So at the end based on

this example I should

have the result "f" as

f <-c(8,32)

appreciate the help,

Andras

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--

Bert Gunter
Genentech Nonclinical Biostatistics

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