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+--- Thread: Plotting periodic function with fft (/thread-38667.html)
Plotting periodic function with fft - schniefen - Nov-10-2022
I want to plot a T-periodic function using a restricted set of Fourier coefficients. The function equals sin(x/tau) for 0<=x<(2*pi*tau) and 0 for (2*pi*tau)<=x<T (it is periodically repeated outside [0,T)). My attempt so far is that I have defined the function as follows:
def p(t,T,tau):
n=np.floor(t/T)
t=t-n*T
if t<(2*np.pi*tau):
p=np.sin(t/tau)
else:
p=0
return p
tdata=np.linspace(-3*np.pi,3*np.pi,500)
pdata=[]
for i in tdata:
pdata.append(p(i,3*np.pi,1))
plt.plot(tdata,np.array(pdata),label='$T=3\pi$, $\u03C4=1$')
plt.legend(loc='upper left')The plotting is just to check that the function as defined is correct and it is (the specified values of the parameters make it easy to double check with a drawing by hand). Anyway, I would now like to plot the function I have plotted using a restricted set of Fourier coefficients. To obtain the coefficients, I would define coefficients=np.fft.fft(np.array(pdata)), but I am unsure how to use these further and plot the function. Appreciate any help.