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octave/matlab codegen wrong for two argument zeta #14820

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cbm755 opened this Issue Jun 22, 2018 · 1 comment

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cbm755 commented Jun 22, 2018

octave_code(zeta(x,n)) should give zeta(n, x).

See: https://www.mathworks.com/help/symbolic/zeta.html

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cbm755 commented Jun 25, 2018

No! This bug is incorrect. Matlab two-arg zeta does the derivative of the Riemann zeta function, whereas ours is the Hurwitz zeta function.

@skirpichev you'll want to revert your fix in diofant too. Maybe you can cherry-pick f9610e9.

There is still a problem in sympy because zeta(x,y) is not implemented in Matlab whereas the current implementation generated "zeta(x, y)". ~~~I will rename this bug...~~~ Update: this bug title is vague enough that its still accurate ;-)

skirpichev added a commit to skirpichev/diofant that referenced this issue Jun 26, 2018

octave codegen: two-arg zeta fcn in Matlab *not* the same as ours
A previous commit mapped `zeta(x, n)` to `"zeta(n, x)"`: this is incorrect
because in Matlab's Symbolic Toolbox, this means the nth derivative of the
Riemann zeta function.  But for us, its the Hurwitz zeta function.
Instead, just mark the two-arg zeta as unimplemented.

Closes sympy/sympy#14820

// edited by skirpichev

@cbm755 cbm755 closed this in #14962 Aug 6, 2018

moorepants pushed a commit that referenced this issue Sep 5, 2018

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