Dear R,

I have a covariates matrix with 10 observations,  e.g.

> X <- matrix(rnorm(50), 10, 5)
> X
             [,1]        [,2]        [,3]        [,4]       [,5]
 [1,]  0.24857135  0.30880745 -1.44118657  1.10229027  1.0526010
 [2,]  1.24316806  0.36275370 -0.40096866 -0.24387888 -1.5324384
 [3,] -0.33504014  0.42996246  0.03902479 -0.84778875 -2.4754644
 [4,]  0.06710229  1.01950917 -0.09325091 -0.03222811  0.4127816
 [5,] -0.13619141  1.33143821 -0.79958805  2.08274102  0.6901768
 [6,] -0.45060357  0.19348831 -1.23793647 -0.72440163  0.5057326
 [7,] -1.20740516  0.20231086  1.15584485  0.81777770 -1.2719855
 [8,] -1.81166284 -0.07913113 -0.91080581 -0.34774436  0.9552182
 [9,]  0.19131383  0.14980569 -0.37458224 -0.09371273 -1.7667203
[10,] -0.85159276 -0.66679528  1.63019340  0.56920196 -2.4049600

And I define a boundary of X:  The smallest "ball" that nests all the
observations of X. I wish to check if a particular point x_i

> x_i <- matrix(rnorm(5), 1, 5)
> x_i
           [,1]      [,2]       [,3]      [,4]      [,5]
[1,] -0.1525543 0.4606419 -0.1011011 -1.557225 -1.035694

is inside the boundary of X or not. I know it's easy to do it with 1-D or
2-D, but I don't knot how to manage it when the dimension is large.

Can someone give a hint? Thanks in advance!


Feng

-- 
Feng Li
Department of Statistics
Stockholm University
106 91 Stockholm, Sweden
http://feng.li/

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