# Plotting sin (x/x) function in terms of Mag(dB) over Frequency

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IFECHUKWU IKE-ORJI on 17 Nov 2022
x=linspace(-20,20);
y= sin(x)./x;
y1 = (10*log(y));
plot(x,y1,'-')
Warning: Imaginary parts of complex X and/or Y arguments ignored.
This is currrently the code i have running but not getting the resulting sin x/x plot, but more so a rectified version of it. i also wanted some help in changing the x axis from linear to frequency(preferably in rad/s), similar to how i changed y from linear to dB.
the sin x/x plot work when using just "plot(x,y)" but now when trying to change the axis to dB and Freq.
;

Paul on 18 Nov 2022
Hi IFECHUKWU,
sin(x)/x can take on negative values, for example
x = 5*pi/4;
sin(x)/x
ans = -0.1801
Taking the log10 (as neeed for dB, not log) of a negative number yields a complex result
log10(ans)
ans = -0.7446 + 1.3644i
Not sure what kind of plot is expected after converting the result dB.
IFECHUKWU IKE-ORJI on 18 Nov 2022
my question was a bit unclear as i was referring to dBm not dB, so you would be right resulting the sin (x/x) waveform being rectified

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