General Form:

linearize vec ...

Create a new plot with all of the vectors in the current plot, or only those mentioned as arguments to the command, all data linearized onto an equidistant time scale.

How to compute the fft from a transient simulation output:

ngspice 8 -> setplot tran1
ngspice 9 -> linearize V(2)
ngspice 9 -> set specwindow=blackman
ngspice 10 -> fft V(2)
ngspice 11 -> plot mag(V(2))tstep

Linearize will redo the vectors vec or renew all vectors of the current plot (e.g. tran3) if no arguments are given and store them into a new plot (e.g. tran4). The new vectors are interpolated onto a linear time scale, which is determined by the values of tstep, tstart, and tstop in the currently active transient analysis. The currently loaded input file must include a transient analysis (a tran command may be run interactively before the last reset, alternately), and the current plot must be from this transient analysis. The length of the new vector is (tstop - tstart) / tstep + 1.5. This command is needed for example if you want to do a fft analysis (17.5.27). Please note that the parameter tstep of your transient analysis (see Chapt. 15.3.9) has to be small enough to get adequate resolution, otherwise the command linearize will do sub-sampling of your signal. If no circuit is loaded and the data have been acquired by the load (17.5.40) command, Linearize will take time data from transient analysis scale vector.