Hi @Stefan Schippers , is it possible to create a time dependent resistor ? Which can change based on some equations w.r.t time from a particular simulation time ? For eg , res = t*res // Thanks

This is more of an ngspice question. The ngspice documentation in section 3.3.4 Resistors, dependent on expressions, says "*Expression* may be an equation or an expression containing node voltages or branch currents (in the form of i(vm)) and any other terms as given for the B source and described in Chapt. 5.1. It may contain parameters (2.8.1) and the special variables time, temper, and hertz (5.1.2)." So, yes, you just want to use

r = 'time*value'

.