find closest value in a vector based on another vector values

From: Bert Gunter <gunter.berton at gene.com>
Subject: Re: [R] find closest value in a vector based on another vector values
To: "Andras Farkas" <motyocska at yahoo.com>
Cc: "Jorge I Velez" <jorgeivanvelez at gmail.com>, "R mailing list" <r-help at r-project.org>
Date: Tuesday, June 18, 2013, 10:55 AM
Andras:

No.
Using the a = c(1,8,9) and b = 2:3 that ** I posted
before**,? you get
the single unique value of 1.

Please stop guessing, think carefully about what you want to
do, and
**test** your code.

-- Bert

On Tue, Jun 18, 2013 at 7:41 AM, Andras Farkas <motyocska at yahoo.com>
wrote:

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