12 lines
422 B
R
12 lines
422 B
R
X=fft(c(1,2,3,4)) # Get the DFT of our signal
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N=4 # Signal size
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xkn=function(k,n){X[k+1]*exp(2i*pi*(k/N)*n)}
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# Perform the inverse DFT:
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x0=1/N*(xkn(0,0)+xkn(1,0)+xkn(2,0)+xkn(3,0))
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x1=1/N*(xkn(0,1)+xkn(1,1)+xkn(2,1)+xkn(3,1))
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x2=1/N*(xkn(0,2)+xkn(1,2)+xkn(2,2)+xkn(3,2))
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x3=1/N*(xkn(0,3)+xkn(1,3)+xkn(2,3)+xkn(3,3))
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x=Re(c(x0,x1,x2,x3)) # Take the real
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stopifnot(any(Im(x)==0)) # Also see how all imaginary parts are 0!
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