I understand. I find this usage, i.e. distinction between
"f" and "f(x)" opaque and confusing, perhaps because I am
used to Mathematica, where the same effect is achieved by
wrapping the function in an "evaluate()" before passing it
to plot().
Kostas
Andrej Vodopivec wrote:
> In plot2d(r4(s),...) you are plotting the expression r4(s):
>
> (%i1) r4(s) := block([s:bfloat(s)], s!/(((s/4)!)^4 * 4^s))$
> (%i2) r4(s);
> (%o2) s!/(4^s*(s/4)!^4)
>
> so you get the same result as you first attempt. r4(s) is computed
> before plot2d starts evaluating in the sample points which are
> therefore not converted to bfloats.
>
> In plot2s(r4,...) you are plotting the function r4. The sample points
> will be converted to bfloats in the function.
>
> Andrej
>
>
>
> On Wed, Mar 11, 2009 at 9:36 PM, Kostas Oikonomou <ko at research.att.com> wrote:
>> Thanks to all for the replies. I like Andrej's solution most.
>> But why doesn't it work if I say
>>
>> plot2d(r4(s), [s,200,300])?
>>
>> "r4" instead of "r4(s)" is confusing.
>>
>> Kostas
>>
>> Andrej Vodopivec wrote:
>>> Use bfloats:
>>>
>>> r4(s) := block([s:bfloat(s)], s!/(((s/4)!)^4 * 4^s));
>>> plot2d(r4, [s,200,300]);
>>>
>>> Andrej
>>>
>>> On Wed, Mar 11, 2009 at 8:36 PM, Kostas Oikonomou <ko at research.att.com>
>>> wrote:
>>>> I have a function
>>>>
>>>> r4(s) := s!/(((s/4)!)^4 * 4^s)
>>>>
>>>> and I am trying to plot it over the range [200,300]:
>>>>
>>>> plot2d(r4(s), [s,200,300])
>>>>
>>>> plot2d returns silently, i.e. it produces nothing. ? I am
>>>> fairly sure the problem is that the computation involves
>>>> intermediate numbers that are too large, although the final
>>>> result is well within the rang of an ordinary float. ?E.g.
>>>> r4(300) is of the order of 10^-4.
>>>>
>>>> I thought I had seen a solution to this kind of problem with
>>>> plot somewhere on the list, but I can't find it. ? It seems
>>>> to me the answer would be worth adding to the documentation
>>>> for plotting.
>>>>
>>>> (This is Maxima 5.17.1 using SBCL, same with CMUCL)
>>>>
>>>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Kostas
>>
>