Confusing results with N[expr]?
- To: mathgroup at smc.vnet.net
- Subject: [mg62318] Confusing results with N[expr]?
- From: "Thomas Bohl" <Thomas.Bohl at cern.ch>
- Date: Sat, 19 Nov 2005 23:19:01 -0500 (EST)
- Organization: CERN
- Sender: owner-wri-mathgroup at wolfram.com
I have the impression that since some time (since Vers. 5.0?) N[expr] does
not give anymore the results I expect.
The following code should illustrate this:
N[a] = 2.;
k = z*(a*Pi);
> 6.28319 z (* "a" and "Pi" are replaced by their numerical value as
> expected *)
k = z^(a*Pi)
> z^(3.14159 a) (* "Pi" is replaced by its numerical value but not "a",
> why not? *)
There are more examples of this behaviour: If the expression is Log[z*a*Pi],
the numerical values of "a" and "Pi" are evaluated, if the expression is
Exp[z*a*Pi] the numerical value of "a" is not evaluated. Why not?
The motivation behind my question is that I was used to write expressions
symbolically and assign numerical values with N[expr] = num. value. This way
you could keep those expressions symbolically and just apply //N when you
needed numerical values. Now it seems that I have lost this possibility.
Could you please comment my observation and maybe suggest a way out?
Thank you very much for any idea.
Prev by Date:
Strange Min/Max result
Next by Date:
Previous by thread:
Re: Strange Min/Max result
Next by thread:
Re: Confusing results with N[expr]?