[R] (no subject)
(Ted Harding)
Ted.Harding at nessie.mcc.ac.uk
Thu Nov 11 21:56:08 CET 2004
On 11-Nov-04 Wei Yang wrote:
> Hi,
>
> I have a list of numbers. For each of the numbers, I take
> sum of squares of the numbers centered on the number chosen.
> If it is less than a certain constant, I will take the
> average of the numbers chosen.
>
> Anyone can give me a sample code. You help will be greatly appreciated.
>
> Peter
Let X = (x1, x2, ... , xn} be your list of numbers.
It seems that what you are looking for is the mean of the set Y:
Y = {y1, y2, ... , ym} such that, for each yj,
yj is in X and sum[over i]( (xi - yj)^2 ) < const
Is this right?
If so, you can do it straightforwardly with a loop, like:
x<-rnorm(100)
const <-150
for( i in (1:100) ) {if(sum(x-x[i])^2<const) Y[i]<-x[i]}
Y[!is.na(Y)]
[1] 0.17096364 -0.32720155 0.19542299 0.13363724
[5] -0.19961480 -0.24486536 -0.31485802 -0.33369635
[9] 0.09981291 0.04263151 0.11127977 0.12144595
[13] -0.27767009 -0.01242218 0.06244776 0.11646301
mean(Y[!is.na(Y)])
[1] -0.04101397
but I'm sure somebody out there will come up with a much
more elegant solution!
Best wishes,
Ted.
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Date: 11-Nov-04 Time: 20:56:08
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