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Re: Working with Indeterminate in large numerical lists

• To: mathgroup at smc.vnet.net
• Subject: [mg100220] Re: Working with Indeterminate in large numerical lists
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Thu, 28 May 2009 06:50:04 -0400 (EDT)
• Organization: Uni Leipzig
• References: <gvlhu1$dos$1@smc.vnet.net>
• Reply-to: kuska at informatik.uni-leipzig.de

Hi,

x /. Indeterminate:> Sequence[]

?

DeleteCases[x,Indeterminate,Infinity]

?

Regards
   Jens

pfalloon wrote:
> Hi everyone,
> I'm wondering about the optimal way to work with Indeterminate in
> large matrices. I've been using this to replace "bad" data points that
> I want to prevent from polluting calculations involving lists of data,
> but I'm not sure I'm working as smartly as I could be.
> 
> As an example, suppose I have a list of machine-precision reals and
> some Indeterminate elements:
> 
> x = RandomSample[Join[RandomReal[1, 1000], ConstantArray
> [Indeterminate, 10]];
> 
> If I want to take only the valid entries, the best I have been able to
> find is something like:
> 
> Select[x, NumberQ]
> 
> This seems to work reasonably well. But if I want to specifically
> select the Indeterminate entries, there doesn't seem to be any
> function (equivalent to, say, "isnan" from another system), so I have to
> resort to something less succinct like
> 
> Select[x, #  === Indeterminate &]
> 
> Does anyone have any suggestions on better ways to do this, or any
> general tips for working with Indeterminate in this context?
> 
> I'm particularly keen to do things in the most efficient way possible
> as I'm working with rather large lists.
> 
> Thanks,
> Peter.
>