Hello Tao_Zhang,
I think it will be less messy to use the 'plotstack' X-Function via lt_exec.
This will let you specify the X and Y pairs and allow you to use all the options that come with the X-Function itself.
import os
import originpro as op
wks = op.new_sheet()
wks.from_file(os.path.join(op.path('e'), 'Samples', 'Graphing', 'Group.dat'))
wks.lt_exec('plotstack iy:=((1,2), (1,3), (1,4))')
For more information on the 'plotstack' X-Function, visit this page:
https://www.originlab.com/doc/X-Function/ref/plotstack
Let me know if this is an appropriate solution for your scenario, and if any other questions arise.
Best,
Nicholas G.
nicholas@originlab.com
OriginLab Technical Support Team