search algorithm

thanks a lot for the help. I tried some stuff and now it works.

____________________
Ita Cirovic-Donev
Risk Controlling

HYPO ALPE-ADRIA-BANK D.D.
Amruseva 6, HR-10000 Zagreb
Phone:      +385 1 4899 269
Fax:  +385 1 6063 344
E-Mail:     ita.cirovic-donev at hypo-alpe-adria.com
Web:  www.hypo-alpe-adria.hr



                                                                           
             Don MacQueen                                                  
             <macq at llnl.gov>                                               
                                                                        To 
             13.02.2006 16:38             Ita.Cirovic-Donev at hypo-alpe-adri 
                                          a.com, r-help at stat.math.ethz.ch  
                                                                        cc 
                                                                           
                                                                   Subject 
                                          Re: [R] search algorithm         
                                                                           
                                                                           
                                                                Importance 
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




There is a function in the Hmisc package that will help.

Example:

 require(Hmisc)
 x <- sort(runif(10))
 x

[1] 0.1225542 0.1620869 0.2197772 0.3187375 0.5498879 0.5644445
0.5812717 0.7380532 0.8187384 0.9063713

 whichClosest(x,.41)

[1] 4

 x[4]

[1] 0.3187375

Or for your matrix (yourmat), this should work (but I haven't tested it)

    yourmat[ whichClosest(yourmat[,'X'] , -0.6523) , 'Y']

-Don

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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--
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA