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Re: Working with Indeterminate in large numerical lists

  • To: mathgroup at smc.vnet.net
  • Subject: [mg100237] Re: Working with Indeterminate in large numerical lists
  • From: dh <dh at metrohm.com>
  • Date: Thu, 28 May 2009 19:35:17 -0400 (EDT)
  • References: <gvlhu1$dos$1@smc.vnet.net>


Hi,

simply try negation:

Select[x, ! NumberQ[#] &]

Daniel





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.

> 




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