[R] search algorithm

[Dimitris Rizopoulos]

maybe something like this could be of help:

mat <- matrix(rnorm(20), 10, 2)
val <- -0.6523
###################
ind <- which.min(abs(mat[, 1] - val))
mat
mat[ind, ]


Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: <Ita.Cirovic-Donev at hypo-alpe-adria.com>
To: <r-help at stat.math.ethz.ch>
Sent: Monday, February 13, 2006 1:30 PM
Subject: [R] search algorithm


>
>
>
>
> Hi!
>
> I have a problem of finding a specific value in a column. For 
> example, I
> have a matrix with say 2 columns
>
>           X                       Y
> 1    -2.0341602   9.036689e-05
> 2    -1.4287230   1.807338e-04
> 3    -1.1194402   2.711007e-04
> 4    -1.0327582   3.614676e-04
> 5    -0.8130556   4.518344e-04
> 6    -0.7138212   5.422013e-04
> 7    -0.6634425   6.325682e-04
> 8    -0.6512083   7.229351e-04
> 9    -0.6176286   8.133020e-04
> 10  -0.5897241    9.036689e-04
>
> Now if I have some value of x=-0.6523. I need to find a value in the 
> X
> column  that is the closest to my value of x then read off the row 
> number
> and then take the corresponding value in column Y. What I am not 
> sure is
> how to do the first search where I would search by decimal places 
> and take
> the smallest absolute distance between the numbers. For example if 
> he finds
> the first value which is correct in this case - and then 0 and then 
> 6 and
> then 5 but now there is no 2 for that specific decimal place so he 
> would
> calculate the distance between the one before and the one after and 
> see
> which one is smaller. For that which is smaller would be the final X 
> value.
> Can someone please give me a hint on how to proceed. Thanks.
>
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