Groups > comp.soft-sys.math.maple > #243 > unrolled thread

Difficulty with simplifying an expression

Started by	rouben@shadow.(none) (Rouben Rostamian)
First post	2011-09-22 20:45 +0000
Last post	2011-09-23 14:05 +0000
Articles	3 — 3 participants

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  Difficulty with simplifying an expression rouben@shadow.(none) (Rouben Rostamian) - 2011-09-22 20:45 +0000
    Re: Difficulty with simplifying an expression Joe Riel <joer@san.rr.com> - 2011-09-22 14:11 -0700
      Re: Difficulty with simplifying an expression rouben@shady.(none) (Rouben Rostamian) - 2011-09-23 14:05 +0000

#243 — Difficulty with simplifying an expression

From	rouben@shadow.(none) (Rouben Rostamian)
Date	2011-09-22 20:45 +0000
Subject	Difficulty with simplifying an expression
Message-ID	<j5g6p1$fv7$1@news.albasani.net>

I have tried this in Maple versions 11 through 14.
Maple refuses to do an obvious simplification.
Here are the details.

Consider the expression "u" produced by:

    with(Statistics):
    X:=RandomVariable(Normal(mu,sigma)); 
    u := AbsoluteDeviation(X,t);

The expression u consists of a sum of three terms and nops(u)
correctly gives 3.  Two of the terms are of the form
"exp(-A) * B * exp(A)" (for some A and B) which should simplify
to B.  Doing "simplify(u)"  or "simplify(expand(u))" does not
help.

The only way I could simplify u was by taking it apart,
simplifying each term, then putting it back together, as in:

   v := expand(u);
   simplify(op(1,v)) + simplify(op(2,v)) + simplify(op(3,v));

Is there a reason why Maple refuses to simplify the original u?

-- 
Rouben Rostamian

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#244

From	Joe Riel <joer@san.rr.com>
Date	2011-09-22 14:11 -0700
Message-ID	<87k4902sf7.fsf@san.rr.com>
In reply to	#243

rouben@shadow.(none) (Rouben Rostamian) writes:

> I have tried this in Maple versions 11 through 14.
> Maple refuses to do an obvious simplification.
> Here are the details.
>
> Consider the expression "u" produced by:
>
>     with(Statistics):
>     X:=RandomVariable(Normal(mu,sigma)); 
>     u := AbsoluteDeviation(X,t);
>
> The expression u consists of a sum of three terms and nops(u)
> correctly gives 3.  Two of the terms are of the form
> "exp(-A) * B * exp(A)" (for some A and B) which should simplify
> to B.  Doing "simplify(u)"  or "simplify(expand(u))" does not
> help.
>
> The only way I could simplify u was by taking it apart,
> simplifying each term, then putting it back together, as in:
>
>    v := expand(u);
>    simplify(op(1,v)) + simplify(op(2,v)) + simplify(op(3,v));
>
> Is there a reason why Maple refuses to simplify the original u?

I cannot answer that, but a simpler way to do what you want is
to use the map command:

map(simplify, v);

-- 
Joe Riel

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#247

From	rouben@shady.(none) (Rouben Rostamian)
Date	2011-09-23 14:05 +0000
Message-ID	<j5i3nu$qsf$2@news.albasani.net>
In reply to	#244

In article <87k4902sf7.fsf@san.rr.com>, Joe Riel  <joer@san.rr.com> wrote:
>rouben@shadow.(none) (Rouben Rostamian) writes:
>>
>>    v := expand(u);
>>    simplify(op(1,v)) + simplify(op(2,v)) + simplify(op(3,v));
>>
>> Is there a reason why Maple refuses to simplify the original u?
>
>I cannot answer that, but a simpler way to do what you want is
>to use the map command:
>
>map(simplify, v);

That's good.  It did not occur to me to apply "map" to
a polynomial.  But the point remains that a plain simplify()
should work but it doesn't, unfortunately.

-- 
Rouben Rostamian

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