From maechler at stat.math.ethz.ch  Mon Jul  5 11:56:58 2010
From: maechler at stat.math.ethz.ch (Martin Maechler)
Date: Mon, 5 Jul 2010 11:56:58 +0200
Subject: [Rd] arr.ind argument to which.min and which.max
In-Reply-To: <4C3049C0.60101@pburns.seanet.com>
References: <4C3049C0.60101@pburns.seanet.com>
Message-ID: <19505.44138.313406.770145@lynne.math.ethz.ch>

>>>>> "PatB" == Patrick Burns <pburns at pburns.seanet.com>
>>>>>     on Sun, 04 Jul 2010 09:43:44 +0100 writes:

    PatB> Is there a reason that 'which.min' and
    PatB> 'which.max' don't have an 'arr.ind'
    PatB> argument?

well,  help(which.min)  tells you that they really were aimed at
doing their job *fast* for vectors.

Of course you are right and a generalization to arrays might be
convenient at times.

    PatB> The context in which I wanted that was
    PatB> a grid search optimization, which seems
    PatB> like it would be reasonably common to me.

well, as the author of these two functions, I can only say

      "patches are welcome!"

and I think should be pretty simple, right ?
You just have to do very simple remapping of the 1d index 'i' back
to the array index, i.e., the same operation
you need to transform seconds into days:hours:minutes:seconds
{{and yes, we old-timers may recall that APL had an operator (I
  think "T-bar") to do that ...}

Martin Maechler, ETH Zurich


    PatB> -- 
    PatB> Patrick Burns
    PatB> pburns at pburns.seanet.com
    PatB> http://www.burns-stat.com
    PatB> (home of 'Some hints for the R beginner'
    PatB> and 'The R Inferno')



[Rd] arr.ind argument to which.min and which.max
Martin Maechler