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Hi..S+ Users:
I have data set below
x<-c(22,10,12,32,20)
> x
[1] 22 10 12 32 20

but y and z are matrix as follow.
First col represents probability and second col represents values.
>y<-matrix(c(0.1,.2,.3,.4,.5,.6,5,10,15,20,25,30),6,2)
>y
     [,1] [,2] 
[1,]  0.1    5
[2,]  0.2   10
[3,]  0.3   15
[4,]  0.4   20
[5,]  0.5   25
[6,]  0.6   30
>z<-matrix(c(.05,.1,.25,.5,.65,.7,.8,.9,2,6,8,10,17,22,35,40),8,2)
>z
     [,1] [,2] 
[1,] 0.05    2
[2,] 0.10    6
[3,] 0.25    8
[4,] 0.50   10
[5,] 0.65   17
[6,] 0.70   22
[7,] 0.80   35
[8,] 0.90   40

I want to find, for each x,  which value of z is closest to each value
of x via y value.
For example, 
x=12,
The result I am looing for would be -
Z=8.

Because the closest value of y to x=8 would be y=10, the probability
corresponding to y=10 would be 0.2.
then, the closest probability of z to the probability(0.2) of y=10
would be 0.25, so the final value of z would be 8

Any comment appreciated.

Jae Ryu
Civil and Environmental Eng.
Univ. of Wash. Seattle, WA