Re: Picking Off Lists That Have No Numbers

• To: mathgroup at smc.vnet.net
• Subject: [mg99556] Re: Picking Off Lists That Have No Numbers
• From: dh <dh at metrohm.com>
• Date: Fri, 8 May 2009 00:12:49 -0400 (EDT)
• References: <gtrl29\$1o5\$1@smc.vnet.net>

```
Hi Gregory,

a pattern _Number matches an expression with Head "Number". But what you

mean is: _?NumberQ.

Daniel

Gregory Lypny wrote:

> Hi everyone,

>

> In a previous thread, "Select and Cases Give Different Answers," I

> discussed a bug, confirmed by others on the list and which Daniel

> Lichtblau of Wolfram said has been fixed in the development kernel,

> and I wonder whether we have the same problem here.

>

> I want to know if a list has no numbers in it.  Here I get the wrong

> answer for the first list.

>

> FreeQ[#, _Number] & /@ {{"NA", 2.3, 3/8}, {"NA", "NA", "NA"}}

>

> yields {True, True}

> And same here.

>

> MemberQ[#, _Number] & /@ {{"NA", 2.3, 3/8}, {"NA", "NA", "NA"}}

>

> {False, False}

>

> If I use Real or Rational for the criterion, I get the right answers,

> but that's no good if you have some lists that are mixtures of strings

> and reals and others that are mixtures of strings and rationals.

>

> FreeQ[#, _Real] && FreeQ[#, _Rational]

> & /@ {{"NA", 2.3, 3/8}, {"NA", "NA", "NA"}, {"NA", 2.3, "NA"}, {"NA",

> 2.3, 9.4}}

>

> Now this works.

>

> Count[#, _String] == Length[#] & /@ {{"NA", 2.3, 3/8}, {"NA", "NA",

> "NA"}}

>

> {False, True}

>

> But this does not!

>

> Count[#, _Number] == 0 & /@ {{"NA", 2.3, 3/8}, {"NA", "NA", "NA"}}

>

> {True, True}

>

> I don't mean to be a pain, but it is important in my sample selection

> procedures to be able to make the distinction between strings and

> numbers, so I'd be interested in knowing whether I'm misunderstanding

> properties such as Number or Numeric (don't really know the

> difference) or this is a bug.

>

>

> 	Gregory

>

```

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