Saving all operating point data for swept simulations

I would like to make plots of gm over Id and I'd like to do that from a SKILL/OCEAN script. I am quite new to cadence and almost completely new to SKILL, so please forgive if some questions have obvious answers.

My problem is that I can only have access to the gm value for the bsim model for the DC operating point, not for all the values.

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; Here's how I set up the analysis:
ocnWaveformTool('wavescan)
simulator('spectre)
design(library cell "schematic")
createNetlist(?recreateAll t ?display nil)
resultsDir(strcat("/local0/scratch/ballinim/xh035/" cell "/spectre/schematic" ))
modelFile(
    '("/usr/local/vlsi/cds/Design_Kits/XFAB_XH035_v3_1/spectre/xh035/mos/param.scs" "3s")
    '("/usr/local/vlsi/cds/Design_Kits/XFAB_XH035_v3_1/spectre/xh035/mos/bip.scs" "tm")
    '("/usr/local/vlsi/cds/Design_Kits/XFAB_XH035_v3_1/spectre/xh035/mos/bsim3v3.scs" "tm")
    '("/usr/local/vlsi/cds/Design_Kits/XFAB_XH035_v3_1/spectre/xh035/mos/cap.scs" "tm")
    '("/usr/local/vlsi/cds/Design_Kits/XFAB_XH035_v3_1/spectre/xh035/mos/dio.scs" "tm")
    '("/usr/local/vlsi/cds/Design_Kits/XFAB_XH035_v3_1/spectre/xh035/mos/ind.scs" "tm")
    '("/usr/local/vlsi/cds/Design_Kits/XFAB_XH035_v3_1/spectre/xh035/mos/res.scs" "tm")
)
saveOption( 'currents "all" )
save('i "/Mn/S" "/Mn/D" "/Mp/S" "/Mp/D")
analysis('dc ?saveOppoint t  ?param "vg"  ?start "0" ?stop "3.3" ?values 0.5
         ?write "spectre.dc"  ?oppoint "rawfile"  ?maxiters "150" ?maxsteps "10000" 
         ?annotate "status"  ?threshold "0.0"  ?detail "node" ?sort "name"  )
temp( 27 )
run()

; Here's how I get a single value for gm
gmoverid = pv("Mn.m1" "gmoverid" ?result "dcOpInfo-info")
printf("gmoverid = %g\n" gmoverid)

; For currents and voltages I get the values for the whole sweep range
id = i("Mn:1" ?result "dc-dc")
vg = v("/vgn" ?result "dc-dc")
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How can I get the value of gmoverid for the whole swept range?

I thought about these possibilities:

1) gmoverid = deriv(id)/id
 but I'm not even sure this is correct because I do not know the bsim model so well.

2) I read somewhere I can specify to spectre to save those things by adding a file with the following text to the model libraries: "save Mn:oppoint". Is there a way to invoke that spectre command directly from the script without writing a file?

3) Iterating the DC analysis with loop. How can I construct a loop for, say, linearly spaced values? In C I would use the for(vg=0;vg

Can please give suggestion?

Thanks.
Marco Ballini