Is there an easy way to change the x axis or should I just run two dc sims? (My attempt failed, below.)

Double sweep DC plots are saved as a single plot, like:

Id   vg    vd
---------------
x    0.00  0
x    0.05  0
x    0.10  0
...
x    1.80  0

x    0.00  0.05
x    0.05  0.05
...
...
x    1.80  1.80

so plotting with vg as sweep variable requires to do some rearranging of the data ordering. A much easier solution is to save two raw files:

dc vd 0 1.8 0.05 vg 0 1.8 0.2
write test_nmos.raw

dc vg 0 1.8 0.05  vd 0 1.8 0.2
write test_nmos1.raw

then in the second graph specify the

test_nmos1.raw

file.