I have the following circuit. I try to find a way to combine the all plots into a single one (like ltspice's .step card). Unfortunately I couldn't get the example from the ngspice's manual working.

I would be grateful if anyone could help me understand the logic behind what I am trying to achieve. I think I need to force my vectors to be stored in a single plot but from my research I found more than one way of doing that (I just cannot understand the logic of those examples so I couldn't adapt them for my circuit)

I use ngspice 35

```
.TITLE AC test

.INCLUDE ../../lib/lm393.sub

x1 in 0 1 0 out lm393

c1 in 0 100n
r1 1 in 100k
c2 out 0 100n
r2 1 out 4.7k

vsup 1 0 DC 5
vin in 0 AC 1

.CONTROL
*foreach x 1n 10n 50n 100n
*    alter c1 = $x
*    ac dec 100 1 100k
*end

alter c2 = 10n
ac dec 100 1 1Meg
alter c2 = 100n
ac dec 100 1 1Meg
alter c2 = 1u
ac dec 100 1 1Meg
alter c2 = 10u
ac dec 100 1 1Meg

plot db(ac1.out) db(ac2.out) db(ac3.out) db(ac4.out)
.ENDC

```