#12922: Implicit derivative
---------------------------------------+------------------------------------
Reporter: mmarco | Owner: burcin
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.10
Component: calculus | Resolution:
Keywords: implicit derivative | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Miguel Marco | Merged in:
Dependencies: | Stopgaps:
---------------------------------------+------------------------------------
Comment (by mmarco):
The problem with using temporary variables without giving them a name
string is this:
{{{
sage: from sage.symbolic.function_factory import SymbolicFunction
sage: var('x,y')
(x, y)
sage: def implicit_derivative(Y,X,F,n=1):
....: x=SR.symbol()
....: yy=SR.symbol()
....: y=SymbolicFunction('y',1)(x)
....: f=SymbolicFunction('f',2)(x,yy)
....: Fx=f.diff(x)
....: Fy=f.diff(yy)
....: G=-(Fx/Fy)
....: G=G.subs_expr({yy:y})
....: di={y.diff(x):-F.diff(X)/F.diff(Y)}
....: R=G
....: S=G.diff(x,n-1)
....: for i in range(n+1):
....: di[y.diff(x,i+1)(x=x)]=R
....: S=S.subs_expr(di)
....: R=G.diff(x,i)
....: for j in range(n+1-i):
....:
di[f.diff(x,i,yy,j)(x=x,yy=y)]=F.diff(X,i,Y,j)
....: S=S.subs_expr(di)
....: return S
....:
sage: implicit_derivative(y,x,x^2+y^2-1)
-D[0](f)(symbol160, y(symbol160))/D[1](f)(symbol160, y(symbol160))
}}}
I don't know why, this problem is not present if we put the strings in the
definitions of the variables.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12922#comment:10>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac?hl=en.
For more options, visit https://groups.google.com/groups/opt_out.
