Thu Jan 21 13:49:18 CET 2010

```Hi,

One approach could be a while loop as follows. Note that your circle
should have radius 0.5 if I understood the problem correctly.

N <- 5

npoints <- 0
ntests <- 0
points.in.circle <- matrix(NA, ncol=2, nrow=N)

while (npoints < N) {

test.point <- runif(2, -0.5, 0.5) # generate new point in 2D
if ( sqrt(test.point %*% test.point) <= 0.5){ # test its distance to
the origin
npoints <- npoints + 1
points.in.circle[npoints, ] <- test.point
}
ntests <- ntests + 1
}

print(paste(npoints, "out of", ntests, 'where in the circle') )

HTH,

baptiste

2010/1/21 Wolfgang Amadeus <fdfcz123 at 163.com>:
> Hello !
>  I have a quick question about loops.
>  For example,  I have a 1 * 1 square and its inscribed circle tangent i, whose radius, of course, is also 1.
>  The loop here is as the following:
>  generate n points, say 5, in the square randomly repeatedly until we have five in total in the circle, then we stop, otherwise we continue.
>  I do not know how !
> Thank you very much for your time.
>  Yours
>
>
>        [[alternative HTML version deleted]]
>
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