Emmanuel wrote: "Please let me know how to comment a ticket, and I will
report this."
I think the usual procedure is to request a TRAC account (the details of
how to request are outlined in the SAGE TRAC homepage).
HTH,
Kannappan
On Fri, Dec 21, 2012 at 8:38 PM, Emmanuel Charpentier <
emanuel.charpent...@gmail.com> wrote:
> Dear Sir,
>
> Thank you for your prompt advice. Some comments below :
>
> Le vendredi 21 décembre 2012 15:03:45 UTC+1, kcrisman a écrit :
>
>>
>>> I am in the process of learning Sage, coming from Maxima (and
>>> Mathematica, which I do not like much...).
>>> Cut'n'pastes from a notebook running on sagenb.org
>>> version()
>>>
>>> version()
>>>
>>>
>>> ==>
>>>
>>> 'Sage Version 5.4, Release Date: 2012-11-09'
>>>
>>> var('t,a,b,d')
>>> ## beta density
>>> dbeta(t,a,b)=t^(a-1)*(1-t)^(b-**1)/beta(a,b)
>>> ## density of the *difference* of two independent beta(1,1)-distributed RVs
>>> ## (yes, I mean uniforms(0 1)...)
>>> integrate(dbeta(t,1,1)*dbeta(**t+d,1,1),t,max(0, -d), min(1,1-d))
>>>
>>> ==>
>>>
>>> 1
>>>
>>> Huh ?? This is seriously whacky :
>>>
>>>
>>>
>> You might want to see what "max(0,-d)" does. The function
>> "max_symbolic" should do what you want, though I don't know whether your
>> integration will work. Hopefully it would.
>>
>
> It does, at least in this special case :
>
> integrate(dbeta(t,1,1)*dbeta(t+d,1,1),t,max_symbolic(0, -d),
> min_symbolic(1,1-d))
>
> ==>
>
> -max(0, -d) + min(1, -d + 1)
>
>
> But why do we have to use max_symbolic ? As far as I can tell, max, like
> many other functions in Sage, could be overloaded to call max_symbolic when
> used with a symbolic argument, no ? After all, we don't have to write
> plus_symbolic(a,b) instead of a+b...
>
>>
>>
>>
>>> dbeta(t,a,b):=t^(a-1)*(1-t)^(**b-1)/beta(a,b)
>>> integrate(dbeta(t,1,1)*dbeta(**t+d,1,1),t,max(0,-d),min(1,1-**d))
>>>
>>> ==>
>>>
>>> dbeta(t,a,b):=t^(a-1)*(1-t)^(**b-1)/beta(a,b)
>>> min(1,1-d)-max(0,-d)
>>>
>>>
>>>
>>
>> I'm also not sure what the := notation would mean here in Sage; that's
>> Maxima style, right?
>>
>
> That's one way to define a function in Maxima (the other being define())
>
>
>> But another one : i tried to give dbeta a proper definition, i. e. with a
>> domain of definition, therefore allowing convolutions :
>>>
>>>
>>>
>>> db2(t,a,b)=Piecewise([[(0,1),**t^(a-1)*(1-t)^(b-1)/beta(a,b)]**])
>>> db2
>>>
>>>
>>
>> You would get this even with
>>
>> db2(x) = Piecewise([[(0,1),x^2]])
>>
>> because piecewise functions do not accept this construction.
>>
>> db2 = Piecewise([[(0,1),x^2]])
>>
>
> Hmm...
>
> db3=Piecewise([[(0,1),dbeta(t,a,b)]],var=t)
> db3
>
> ==>
>
> Piecewise defined function with 1 parts, [[(0, 1), t |--> (-t + 1)^(b -
> 1)*t^(a - 1)/beta(a, b)]]
>
>
> Not so good : db3 is a function of one variable, with no second or third
> argument.
>
>>
>> works. Unfortunately, I'm not so sure the three-variable equivalent is
>> much better here, as this (now very old) class was designed for
>> single-variable constructs (though it does support convolution in that
>> context). You may want to use pw.mac inside Maxima for this, I'm not sure.
>> Or there might be a way to trick a lambda function to make this work.
>>
>> I'm sorry that our piecewise support is not the greatest. It's a
>> longstanding annoyance.
>>
>
> I saw a ticket relating to it. I wanted to comment, but was unable to find
> *how* to comment a ticket (or open another, by the way).
>
> In my exploration of tickets about symbolics, I found also
> http://trac.sagemath.org/sage_trac/ticket/3745, which I wanted to
> comment. The reported problem still stands in maxima 5.26, current with
> Sage, but is slightly alleviated in maxima 5.29. Further exploration also
> showed workarounds in current Sage. Please let me know how to comment a
> ticket, and I will report this.
>
>>
>> - kcrisman
>>
>> --
> You received this message because you are subscribed to the Google Groups
> "sage-support" group.
> To post to this group, send email to sage-support@googlegroups.com.
> To unsubscribe from this group, send email to
> sage-support+unsubscr...@googlegroups.com.
> Visit this group at http://groups.google.com/group/sage-support?hl=en.
>
>
>
--
You received this message because you are subscribed to the Google Groups
"sage-support" group.
To post to this group, send email to sage-support@googlegroups.com.
To unsubscribe from this group, send email to
sage-support+unsubscr...@googlegroups.com.
Visit this group at http://groups.google.com/group/sage-support?hl=en.
