Im trying to lambdify this function
def f(x):
if ceil(x)%2 == 0:
return -1
else :
return +1
a = sympy.lambdify(x,f(x))
Im getting an error when i try to do that. I also tried piecewise , but it is not giving me the desired outcome
y = lambdify(x,(Piecewise((1, ceil(x)%2 == 0), (-1,True))))
Please help Thanks in advance
You need to pass a symbolic expression to lambdify so a Python function is no good. Also you need to use symbolic sympy functions and sympy's ceil function is actually called ceiling. Finally == compares if two expressions are the same which is not the same as constructing a symbolic Boolean. For that you need Eq:
That gives
In [19]: p = Piecewise((1, Eq(ceiling(x)%2, 0)), (-1,True))
In [20]: p
Out[20]:
⎧1 for ⌈x⌉ mod 2 = 0
⎨
⎩-1 otherwise
In [21]: y = lambdify(x, p)
In [22]: y([1, 2, 3])
Out[22]: array([-1., 1., -1.])
References:
https://docs.sympy.org/latest/modules/functions/elementary.html#ceiling https://docs.sympy.org/latest/tutorial/gotchas.html#equals-signs