On Sun, 24 Dec 2006, Hugo Coolens wrote:
>
>
>
> On Sat, 23 Dec 2006, Barton Willis wrote:
>
>> For big 'm', your calculation suffers from subtractive
>> cancelation; try bfloat instead of float:
>>
>> (%i11) huge : gain(61,%i*2*%pi*60)$
>> (%i12) bfloat(huge), fpprec : 123;
>> (%o12) 1.1462233314862319837372937172[66
>> digits]7101238230788110302499429193b0
>> (%i13) float(huge);
>> (%o13) 0.0
>>
>> Barton
> thanks a lot, this solves the mystery and helps me further
>
> best regards,
> hugo
>
Unfortunately with higer values of m something goes wrong:
bfloat(gain(100,%i*2*%pi*177.828)), fpprec : 123;
lots of the following warnings and then an error message:
Warning: Float to bigfloat conversion of ....
Maxima encountered a Lisp error:
Error in MACSYMA-TOP-LEVEL [or a callee]: Can't print a non-number.
Automatically continuing.
To reenable the Lisp debugger set *debugger-hook* to nil.
any idea how to solve this?
regards,
Hugo
>
>>
>> -----maxima-bounces at math.utexas.edu wrote: -----
>>
>>> To: Barton Willis
>>> From: Hugo Coolens
>>> Sent by: maxima-bounces at math.utexas.edu
>>> Date: 12/23/2006 02:43PM
>>> cc: maxima at math.utexas.edu
>>> Subject: Re: [Maxima] newbie question, forcing
>>> numeric result
>>>
>>>
>>>
>>>
>>> On Sat, 23 Dec 2006, Barton Willis wrote:
>>>
>>>> Try *something* like
>>>>
>>>> (%i1) mypow(a,b) := if a=0 and b= 0 then 1 else
>>> a^b;
>>>> paldn(m,s) :=
>>>>
>>> (sum(binomial(2*m-i,i)*mypow(s,i),i,0,m-1))/(sum(
>>> binomial(2*m-i,i)*mypow(s,i),i,0,m));
>>>>
>>>> gain(m,s) := abs(paldn(m,s));
>>>> pairs: makelist([0.1*omega,
>>> gain(2,%i*omega)],omega,0,5);
>>>>
>>>> (%o1) mypow(a,b):=if a=0 and b=0 then 1 else
>>> a^b
>>>> (%i2)
>>>> (%o2)
>>>>
>>> paldn(m,s):=sum(binom(2*m-i,i)*mypow(s,i),i,0,m-1
>>> )/sum(binom(2*m-i,i)*mypow(s,i),i,0,m)
>>>>
>>>> (%i3)
>>>> (%o3) gain(m,s):=abs(paldn(m,s))
>>>> (%i4)
>>>> (%o4)
>>>>
>>> [[0,1],[0.1,sqrt(10)/3],[0.2,sqrt(37)/(3*sqrt(5))
>>> ],[0.3,sqrt(82)/sqrt(145)],[0.4,sqrt(145)/(3*sqrt
>>> (41))],[0.5,sqrt(226)/(3*sqrt(89))]]
>>>>
>>>> (%i5)
>>>>
>>>> Notes:
>>> thanks for the instructive reply, strange enough
>>> I am confronted now with
>>> another problem. The above defined function
>>> gain(m,s) stops functioning
>>> correctly when m>=60 as you can see below. It is
>>> a complete mystery to me
>>> why this happens:
>>>
>>> (%i19) float(gain(59,%i*2*%pi*60));
>>>
>>> (%o19) 1.14706260261368
>>>
>>> (%i18) float(gain(60,%i*2*%pi*60));
>>>
>>> (%o18) 0.0
>>>
>>> (%i20) float(gain(61,%i*2*%pi*60));
>>>
>>> (%o20) 0.0
>>> _______________________________________________
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>>> Maxima at math.utexas.edu
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>>> a
>>
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