Sympy unable to plot Fourier series, bug

[Areeb Sherjil]

Hi all, 

I hope everyone is enjoying themselves!

I am trying to compute the Fourier series of a simple signal(1 Volt square with freq of 1hz and 0.5T pulse width). 

This is what I need help with:

1- How can I make sympy display the results of the sigma summation as : Ao+An1+An2+An3....... etc instead of the way it now?Like how do I expand it?

2- When I try to plot this, I get a warning message telling me to report this as a bug? Why is this ?(look at screenshot)

Any response is very much appreciated 

All necessary file attached(CODE:https://drive.google.com/file/d/17W3GqiN0x1oByMdgAiZHssGNu2aCJdPV/view?usp=sharing)

[Areeb Sherjil]

No one is replying, lemme paste the code here:

import sympy as syms

import matplotlib.pyplot as plot

import numpy as linspace

n,t= syms.symbols('n,t')

T= 1

w= 2*syms.pi/T

V=1   # square wave of 1volts with 1second period

Ao= (w/syms.pi)* syms.integrate(V,(t,0,0.5))

An= (w/syms.pi)*syms.integrate(V*syms.cos(w*n*t),(t,0,T/2))

Bn= (w/syms.pi)*syms.integrate(V*syms.sin(w*n*t),(t,0,T/2))

f= Ao/2 +syms.Sum(An*syms.cos(n*w*t),(n,1,5))+ syms.Sum(Bn*syms.sin(n*w*t),(n,1,5))

f

syms.plot(f,(t,0,2*T))

[Davide Sandona']

Whenever it makes sense, you should use assumptions on symbols. Since you are dealing with a Fourier Series, you should set:

import sympy as syms
import matplotlib.pyplot as plot
import numpy as linspace

n = syms.symbols('n', real=True, integer=True, positive=True)
t = syms.symbols('t', real=True)

T= 1
w= 2*syms.pi/T
V=1   # square wave of 1volts with 1second period
Ao= (w/syms.pi)* syms.integrate(V,(t,0,0.5))
An= (w/syms.pi)*syms.integrate(V*syms.cos(w*n*t),(t,0,T/2))
Bn= (w/syms.pi)*syms.integrate(V*syms.sin(w*n*t),(t,0,T/2))
f= Ao/2 +syms.Sum(An*syms.cos(n*w*t),(n,1,5))+ syms.Sum(Bn*syms.sin(n*w*t),(n,1,5))
f

At this point, the expression f looks like can be simplified. Then:

syms.plot(f.simplify(), (t, 0, 4*T))

Davide.

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[Areeb Sherjil]

Respond to  Davide

Hi,

Thanks for this.

1-I want to ask: how do I expand the sigma summation like : cos+cos2+cos3..... etc 

2- Also how do I open the plot in a separate window to make it bigger/zoom etc?

[Areeb Sherjil]

Oh no sorry, I used %matplotlib tk at the start and now it opens the graph in separate window.(Google groups does not allow to edit messages )

But how to expand the summation series?

[Davide Sandona']

Use the doit() method, something like the following: f.doit()

Davide.

To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/51ab68de-b41b-4fce-9b41-e428d2c8d42dn%40googlegroups.com.

[Areeb Sherjil]

Thanks  Davide!

It works now