Re: [R] search algorithm

From: Dimitris Rizopoulos <dimitris.rizopoulos_at_med.kuleuven.be>
Date: Mon 13 Feb 2006 - 23:55:11 EST

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


>
>
>
>
> 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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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Mon Feb 13 23:58:35 2006

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