I can do
f(a,b) = a^2+b^3; f=f-f.subs(a=(a-1))
(a, b) |--> -(a - 1)^2 + a^2
I tried to write a function which does this for arbitrary expressions and variables
def test(self, symb):
return (self-self.subs(symb=(symb-1)))
but
test(f,a)
(a, b) |--> 0
fails miserably. It seems self.subs(symb=(symb-1)) can not be evaluated properly. How can I achieve what I want?
Just double the equal sign in the substitution:
sage: f(a,b) = a^2+b^3
sage: def test(self, symb):
....: return (self-self.subs(symb==(symb-1)))
sage: test(f,a)
(a, b) |--> -(a - 1)^2 + a^2
Note that you can also use Python dicts instead of symbolic expressions, which is usually more robust for complex substitutions :
sage: def test(self, symb):
....: return self-self.subs({symb: symb-1})
Asked: 2020-04-10 18:53:00 +0100
Seen: 273 times
Last updated: Apr 14 '20
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