#9130: Access to beta function
---------------------------------------------+------------------------------
Reporter: kcrisman | Owner: burcin
Type: enhancement | Status: positive_review
Priority: major | Milestone: sage-5.0
Component: symbolics | Keywords: special
function, pynac, sd35.5
Work_issues: | Upstream: N/A
Reviewer: Benjamin Jones, Burcin Erocal | Author: Karen T. Kohl,
Burcin Erocal
Merged: | Dependencies:
---------------------------------------------+------------------------------
Changes (by burcin):
* status: needs_work => positive_review
Old description:
> Although Maxima has the beta function, Sage doesn't:
> {{{
> sage: a, b, c = var('a b c')
> sage: assume(a > 0)
> sage: assume(b > 0)
> sage: x = var('x')
> sage: beta_dist = x**(a-1) * (1 - x)**(b-1)
> sage: c = integral(beta_dist, x, 0, 1)
> sage: c
> beta(a, b)
> sage: c(a=.5,b=.5)
> beta(0.500000000000000, 0.500000000000000)
> sage: c(a=.5,b=.5).n()
> ---------------------------------------------------------------------------
> TypeError Traceback (most recent call
> last)
>
> /Users/karl-dietercrisman/<ipython console> in <module>()
>
> /Users/karl-dietercrisman/Desktop/sage-4.4.2/local/lib/python2.6/site-
> packages/sage/symbolic/expression.so in
> sage.symbolic.expression.Expression.n
> (sage/symbolic/expression.cpp:17042)()
>
> TypeError: cannot evaluate symbolic expression numerically
> }}}
> This *is* is Ginac, though, and there is even room for defining it in
> symbolic/expression.pyx . It probably is also included in some of our
> other libraries, as a standard special function.
>
> ----
>
> Apply
> * [attachment:trac_9130_combined.2.patch]
New description:
Although Maxima has the beta function, Sage doesn't:
{{{
sage: a, b, c = var('a b c')
sage: assume(a > 0)
sage: assume(b > 0)
sage: x = var('x')
sage: beta_dist = x**(a-1) * (1 - x)**(b-1)
sage: c = integral(beta_dist, x, 0, 1)
sage: c
beta(a, b)
sage: c(a=.5,b=.5)
beta(0.500000000000000, 0.500000000000000)
sage: c(a=.5,b=.5).n()
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/Users/karl-dietercrisman/<ipython console> in <module>()
/Users/karl-dietercrisman/Desktop/sage-4.4.2/local/lib/python2.6/site-
packages/sage/symbolic/expression.so in
sage.symbolic.expression.Expression.n
(sage/symbolic/expression.cpp:17042)()
TypeError: cannot evaluate symbolic expression numerically
}}}
This *is* is Ginac, though, and there is even room for defining it in
symbolic/expression.pyx . It probably is also included in some of our
other libraries, as a standard special function.
----
Apply
* [attachment:trac_9130-beta_function.patch]
* [attachment:trac_9130-py_float_segfault.take2.patch]
--
Comment:
I uploaded a new patch which combines Karen's previous patches. This is
ready to go now.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9130#comment:24>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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