Hi there, given a numeric vector, I can select numbers within a specific range. However presently, I have something related but different problem. Suppose I have a numeric vector. Now take an arbitrary number. Goal to to chose a specific subset with a given length, from that given vector, so that those chosen numbers are centered around that given constant. Here is one example: ### My original vector Vec <- rnorm(1000) ### Now chose some arbitrary number Number <- 0 ### Chose the length of the resulting vector New.Len <- 10 Now I have to chose 10 numbers from 'Vec' around 'Number'. If my 'Vec' contains one or more zero then those zero(s) also be selected. Can somebody help me with some pointer how can I achieve that? Thanks,
On Jul 8, 2011, at 3:16 PM, Nipesh Bajaj wrote:> Hi there, given a numeric vector, I can select numbers within a > specific range. However presently, I have something related but > different problem. Suppose I have a numeric vector. Now take an > arbitrary number. Goal to to chose a specific subset with a given > length, from that given vector, so that those chosen numbers are > centered around that given constant. > > Here is one example: > > ### My original vector > Vec <- rnorm(1000) > > ### Now chose some arbitrary number > Number <- 0 > > ### Chose the length of the resulting vector > New.Len <- 10 > > Now I have to chose 10 numbers from 'Vec' around 'Number'. If my 'Vec' > contains one or more zero then those zero(s) also be selected.An odd number of values would be easier to "center" around the closest to zero value. Here is a reduced example that picks out the 7 values (3 on either side of the closest to zero whose order statistic is closest to the value closest to zero: > x <- rnorm(20) # Sorry, forgot to set.seed() > ?which min > sort(x)[which.min(abs(sort(x))] # closest to zero is the 9th value in sort(x) > sort(x)[(which.min(abs(sort(x)))-3):(which.min(abs(sort(x)))+3)] [1] -0.15579551 -0.05612874 -0.04493361 -0.01619026 0.07456498 0.38984324 [7] 0.41794156 -- David Winsemius, MD West Hartford, CT
Hi:
Do you want the N points in the vector closest to a fixed point? If
so, then try this:
f <- function(vec, center, nselect) {
d <- (vec - center)^2
vec[order(d)][1:nselect]
}
v <- rnorm(1000)
f(v, 0, 10) # select the ten points in v closest to zero
Your goal is subject to multiple interpretations, so if this is not
what you require, perhaps you should sharpen your question.
HTH,
Dennis
On Fri, Jul 8, 2011 at 12:16 PM, Nipesh Bajaj <bajaj141003 at gmail.com>
wrote:> Hi there, given a numeric vector, I can select numbers within a
> specific range. However presently, I have something related but
> different problem. Suppose I have a numeric vector. Now take an
> arbitrary number. Goal to to chose a specific subset with a given
> length, from that given vector, so that those chosen numbers are
> centered around that given constant.
>
> Here is one example:
>
> ### My original vector
> Vec <- rnorm(1000)
>
> ### Now chose some arbitrary number
> Number <- 0
>
> ### Chose the length of the resulting vector
> New.Len <- 10
>
> Now I have to chose 10 numbers from 'Vec' around 'Number'.
If my 'Vec'
> contains one or more zero then those zero(s) also be selected.
>
>
> Can somebody help me with some pointer how can I achieve that?
>
> Thanks,
>
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