Hi Everyone, I'd like to compute multivariate integrals that contain Dirac Deltafunctions. I.e. expressions like
integrate(exp(-(x**2+y**2))/pi * delta(2*x+3*y), (x,-oo, oo), (y,-oo, oo)) The deltaintegrate function inside sympy fails to compute these correctly, see issue 2630. <http://code.google.com/p/sympy/issues/detail?id=2630> Wikipedia says<http://en.wikipedia.org/wiki/Dirac_delta_functions#Properties_in_n_dimensions>that you can compute general expressions of this form as follows: [image: \int_{\mathbb{R}^n} f(\mathbf{x}) \, \delta(g(\mathbf{x})) \, d\mathbf{x} = \int_{g^{-1}(0)}\frac{f(\mathbf{x})}{|\mathbf{\nabla}g|}\,d\sigma(\mathbf{x})] (hopefully the above image makes it through, if not go here) http://upload.wikimedia.org/wikipedia/en/math/3/3/f/33fbbed28ec715257d268faefc9e0e9f.png How hard would it be to compute the right hand side in sympy? In particular I'm confused by how to express the domain and what they mean by \delta\sigma(x) Or, if there is a better way of going about this I'm happy to hear it. -Matt -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
