Hello, I would like to know if it is possible to do a "complicated" Monte Carlo simulation in Xschem/NGspice. This would be a transient simulation where the result is the frequency of an oscillating signal at the output. (Before, I was measuring this frequency "by hand" by plotting the signal but this is clarly unfeasable for Monte Carlo)

I think you can run many transient runs and measure the period of the waveform automatically in ngspice by using .meas commands. See the manual. You can then create a vector with the measured period or its inverse (frequency) and save the data.

Ok thank you

There is a project example in the ngspice distribution, see git at https://sourceforge.net/p/ngspice/ngspice/ci/master/tree/examples/Monte_Carlo/MC_ring_ts.sp .