on 05/09/2008 08:07 AM Esmail Bonakdarian wrote:
Hello,
which.max() only returns one index value, the one for the
maximum value. If I want the two index values for the two
largest values, is this a decent solution, or is there a
nicer/better R'ish way?
max2 <-function(v)
{
m=which.max(v)
v[m] = -v[m]
m2=which.max(v)
result=c(m, m2)
result
}
Seems to work ok.
Thanks,
Esmail
I might be tempted to take a more generic approach, where one can
provide an argument to the function to indicate that I want the 'top x'
maximum values and to give the user the option of returning the indices
or the values themselves.
Perhaps:
which.max2 <- function(x, top = 1, values = FALSE)
{
if (values)
rev(sort(x))[1:top]
else
order(x, decreasing = TRUE)[1:top]
}
set.seed(1)
Vec <- rnorm(10)
> Vec
[1] -0.6264538 0.1836433 -0.8356286 1.5952808 0.3295078 -0.8204684
[7] 0.4874291 0.7383247 0.5757814 -0.3053884
> which.max2(Vec, 2)
[1] 4 8
> which.max2(Vec, 2, values = TRUE)
[1] 1.5952808 0.7383247
HTH,
Marc Schwartz
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