Help me in yt eosacro tutorials for absolute beginners

[Jackie100Sm]

Please help me out , I'm an absolute beginner in Houdini 17 without any prior knowledge in 3D softwares , I was following this Tutorial Series from "eosacro" in Houdini , I was doing fine until I stumbled upon this particular video "Intro to polygons" 

 , the last portion of groupings is really hard as there's no option for "group by expression" in houdini 17 . ANY FORM OF HELP WILL BE REALLY , GRATEFULLY APPRECIATED 

[bunker]

you can create groups with an expression in an attribute Wrangle (run on Primitives)

if(v@N.y<0)@group_reverse=1;

or if you set your normals on primitives, you can type directly @N.y<0 in the Source Group or the Reverse SOP

groupexpression_001.hipnc

Edited December 29, 2018 by bunker

[Noobini]

or rclick (or tab), group....then pick Group Expression...the red hat ?

[bunker]

yeah, I forgot about that one, even less typing:
the Group Expression SOP creates similar VEX code in the end:
VEXpression: @N.y<0
generated created: @group_group1 = @N.y<0;