You probably have to pass in the "dx" as a local variable, i.e. do
something like
sage_stuff = sage_eval(expr, locals = {'dx' = 'dx'})
where expr is your mathematica expression.
-Marshall Hampton
On Aug 14, 1:49 pm, Viny <hje...@hotmail.com> wrote:
> Thanks for your help Felix, with your ideas i made progresses. But the
> problem isn't fixe yet. Since i have some symbolic variable such 'dx'
> in my expressions, the
> code's line --> 500 return eval(string, {'I': numpy.complex(0,1)})
> generate this folowing error
> NameError: name 'dx' is not defined
> Even when i put in the begining of my function var ("dx"), the problem
> stay.
>
> Thanks again
>
> On 14 août, 04:04, thelamecamel <thelameca...@gmail.com> wrote:
>
> > Hi Viny,
>
> > Sage's mathematica support at present seems to be geared towards
> > sending data to mathematica and printing the results to the screen,
> > rather than getting mathematica's results back into sage for data
> > manipulation. So the going may be a little rough.
>
> > Sage can convert its own arrays into mathematica's notation, e.g.
> > Jason's example
> > sage: b=mathematica([1,2,3])
> > will create a mathematica variable representing the array {1,2,3},
> > accessible from sage. I'm not sure whether you can send mathematica
> > more complicated things such as functions in this fashion.
>
> > Once you've got your variables into mathematica, you perform
> > mathematica functions on them like so:
> > sage: x = mathematica(1)
> > sage: mathematica.eval('myfunc[x_,y_]:=x+y')
> > sage: x.myfunc(2)
> > 3
>
> > It's hard to get your mathematica results back into sage for use. As
> > Jason noted below, mathematica arrays with {} don't get converted back
> > into sage arrays with []. There is a ticket related to the array
> > problem <http://trac.sagemath.org/sage_trac/ticket/4948>, but there
> > seems to be no progress on it.
>
> > I gave up and rolled my own mathematica list to numpy array conversion
> > - you might find it useful. I believe that using eval() is frowned
> > upon for security reasons. If you want sage arrays rather than numpy
> > arrays, then use sage_eval() (which is considerably slower for large
> > arrays) and strip out the numpy stuff. Comments on the below code are
> > welcome.
>
> > import numpy
> > import re
> > def mma_to_numpy(mma_arr):
> > """Convert mathematica array to numpy array."""
> > # Convert the mathematica object to a string
> > string = repr(mma_arr)
> > # Convert mathematica-style {} to python style []
> > string = string.replace('{','[').replace('}',']')
> > # Replace mathematica's crazy exponent notation with the standard
> > one
> > string = string.replace('*^', 'e')
> > # Delete new lines (both \n and \r\n appear sporadically)
> > string = string.replace('\n', ' ').replace('\r', ' ')
> > # Detect characters that should not be in an array
> > if re.findall(r'[a-df-zA-HJ-Z]+', string) != []:
> > raise TypeError, "Mathematica returns non-array: %s" % string
> > # Read the string into numpy, interpreting I as j
> > return eval(string, {'I': numpy.complex(0,1)})
>
> > You use it as such:
> > sage: b = mathematica([1.5,2.+3.j,3])
> > sage: b
> > {1.5, 2. + 3.*I, 3}
> > sage: numpy.array(mma_to_numpy(b), dtype='D')
> > array([ 1.5+0.j, 2.0+3.j, 3.0+0.j])
>
> > Hope that this helps - there isn't much documentation on this stuff.
>
> > Cheers,
> > Felix
>
> > On Aug 13, 8:26 pm, Viny <hje...@hotmail.com> wrote:
>
> > > On 13 août, 10:47, Viny <hje...@hotmail.com> wrote:
>
> > > > Hi,
>
> > > > I have a problem of memory into maxima when it performs a symbolic
> > > > expression of an hessian matrix. This symbolic expression of the
> > > > hessian seems to be too big. My sage program is written using python.
> > > > And i want to compute the hessian matrix with mathematica 6.0 in my
> > > > sage file.
> > > > I need to compute symbolic expresstion of the gradient and the hessian
> > > > with mathematica and after compute the mathématica LinearSolve
> > > > function to solve hessian^-1*grad.
> > > > How to make this interface in my .sage?
> > > > Please help me!!!
>
> > > > I have mathematica 6.0 and sage4.0.2 in my linux 64bit system.
>
> > > This is an example of the function to compute the gradient in
> > > my .sage, but it doesn't work.
> > > def grad(f,v):
> > > return mathematica ( f ).D( [ ' v ',1] )
> > > The result is {0,0} . I have another problem of format, i don't know
> > > the command to change { } in () in the mathematica result {0,0}
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