Numpy warning:Casting Complex to real discards imaginary part

Question

i am trying a Matlab code in Python

my code gives a warning

/usr/lib/python2.7/dist-packages/numpy/core/numeric.py:235: ComplexWarning: Casting complex values to real discards the imaginary part

return array(a, dtype, copy=False, order=order)

Python Code

demod_1_a=mod_noisy*2*cos((2*pi*Fc*t)+phi)

N=10
Fc=40
Fs=1600
d=firwin(numtaps=N,cutoff=40,nyq=Fs/2)
print(len(d))
Hd=lfilter( d, 1.0, demod_1_a)
print(len(Hd))
y2=(convolve(Hd,raised))/Convfac
print(len(y2))
y2=y2[(sa/2)-1:-sa/2]
print(len(y2))
demod_3_a=y2[(sa/2)-1::sa]
print(len(demod_3_a))

demod_1_b=-1*mod_noisy*2*sin((2*pi*Fc*t)+phi)

Hd2=lfilter(d,1.0,demod_1_b)

y3=(convolve(Hd2,raised))/Convfac

y3=y3[(sa/2)-1:-sa/2]

demod_3_b=y3[(sa/2)-1::sa]

#########3333
#Demod

demod=demod_3_a+(1j)*demod_3_b
print((demod))
plot(demod,'wo')
show() 

this code is giving me results but not desired results.i wanted to ask that how does this warning will effect my Code? and what is the solution to get rid out of this warning.Please help

Answer 1

The warning is coming from the plot command -- I'm pretty sure. "plot" is meant to take a 1d, real array and put it on the screen. When it sees an array of complex numbers it does the best it can, i.e. discards the imaginary part and plot the real part.

You might want to try something like

plot(numpy.real(demod),'wo')
plot(numpy.imag(demod),'wo')

if you want to see both parts.