[R] search algorithm

[Ita.Cirovic-Donev@hypo-alpe-adria.com]

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.