Is there a better way to get the index of a minimum?

Question

Consider the following reproducible example:

# note that lh is a standard ts dataset that ships with R 
lh
# fit an R model 
ar.mle<-ar(lh,method="mle")
# now get the min AIC, this is the relevant line:
ar.mle$aic[ar.mle$aic==min(ar.mle$aic)]

This works fine and gives back the smallest AIC value and it's index, which is the suggested AR order. I feel I am repeating myself in this last line of code. Is there an easier way to obtain index and value? I know I could use partial autocorrelations to determine the level, too. This is not a stats question, but an R indexing question.

• Carl Witthoft: Try which([blahblah], arr.ind=TRUE)

Answer 1

perhaps the function which.min() would do the trick?

which.min(ar.mle$aic)

it won't shorten your code all that much:

ar.mle$aic[which.min(ar.mle$aic)]

• ran2: nice start tim :)

Answer 2

Well, it really doesn't return an index and value, what you get is a named value.

> ans <- ar.mle$aic[which.min(ar.mle$aic)]
> names(ans)
[1] "3"

The index itself is actually 4 (and is an integer); R indexes from 1.

> which.min(ar.mle$aic)
3
4
> which.min(ar.mle$aic) == 4
 3
TRUE

(yes, this idea of tagging names to values is rather weird, coming from any other language)