1
someone can help me, please?
I’m trying to write a function in Python (I use 3) that implements the following code that is in Mathematica:
Source:[https://rip94550.wordpress.com/2009/05/13/n-6-scaling-functions-and-mother-wavelets/]
Basically, the problem is this: I need to determine a Phi(t) function over the range [0.5] given the following conditions:
a) Phi(0), Phi(1), Phi(2), Phi(3), Phi(4) and Phi(5) are known.
b) actual K0, K1, K2, K3, K4 and K5 constants are also known.
b) the Phi(t) function is defined recursively:
Phi(t) = sum(ki*Phi(2t-i)) = K0*Phi(2t) + K1*Phi(2t-1) + K2*Phi(2t-2) + K3*Phi(2t-3) + K4*Phi(2t-4) + K5*Phi(2t-5)
I tried using the sympy module creating a polynomial that represented Phi(t):
def phi(h,t):
norm = math.sqrt(2)
string = '0 +'
for k in range(len(h)):
parameter = norm*h[k]
string_aux = f'({parameter}*phi[2*t-{k}])+'
string = string + string_aux
string = string[:-1]
pol1 = sym.sympify(string)
where h is the set of parameters I placed above (item b).
When executing entering the variable "t" previously declared using
t = sympy.symbols('t')
I get the following error:
TypeError: 'Symbol' object is not subscriptable
I don’t know if this is the best way to implement this function because it is still recursive. Can you help me with this error and with the proper implementation of this problem? Thank you all.
Review the indentation of the function
phi().– Augusto Vasques
@Augustovasques in my code she is identada. Thanks for the remark. I will correct here. Hugs.
– Luciano Magrini
Correct, because just as I did someone else can look at the indentation and recommend closing the question. I’m withdrawing my recommendation as soon as the issue is made.
– Augusto Vasques
@Augustovasques correction made! Thank you.
– Luciano Magrini
I didn’t find that line
t = sympy.symbols('t')within the functionphi(). I ask you are trying to create a symbol over a local function parameter in a scope outside the function? If it is has no way, that parametertcan only be accessed within the body of the function.– Augusto Vasques
@Augustovasques is just that. I’m trying to create outside the function. In general this variable t will appear in other functions also that I’m creating. From what you’re telling me for each of them I need to declare internally, right? I’ll try to do it here. Thank you.
– Luciano Magrini
@Augustovasques includes the line
t = sympy.symbols( ' t ' )between the last and penultimate line but the error has not changed. Remains identical.– Luciano Magrini
The error is not on the line
t = sympy.symbols('t'). The error is happening on the linepol1 = sym.sympify(string)there is something wrong with the generated expression0 +(0.0*phi[2*t-0])+(1.4142135623730951*phi[2*t-1])+(2.8284271247461903*phi[2*t-2])– Augusto Vasques
@Augustovasques I’ll think a little bit more about that line. Thanks. EDIT: One thing I’ve already found. The line that defines
pol1 = sym.sympify(string) tem algo de errado na expressão gerada 0 +(0.0*phi[2*t-0])+(1.4142135623730951*phi[2*t-1])+(2.8284271247461903*phi[2*t-2])...is wrong. I should not use brackets. I should use brackets. Editing in my question...– Luciano Magrini