I'm trying to extract imaginary information from a dft of transient data to look at the steady state information on a driven circuit. To make sure this works, I started with a pss analysis, because I assume that the pss_fd and pss_td are the exact same data, just in different formats. In other words, I assume that you could reconstruct the time domain waveform from just the frequency/phase information.
The information I get from imag( v("/top" ?result 'pss_fd)) is correct. However, when I plot imag( dft( v("/top" ?result 'pss_td ) 0 stop 16 "Rectangular" 1 "default" 1.0)) does not give the same data.
I did a simple test case of a single sinusoidal source, and the above does seem to work. However, with a much more complicated circuit, it does not.
Is this a misunderstanding on my part of the dft? I admit, I'm not an expert on FFTs.