Anyone know how to set up something similar to Maya's circularize component ?

If you have group of primitives, I would calculate the average Normal and Position to planarize the selection. Now you can calculate for each point the distance from the center to the border to get the radius ratio. The radius of circle should the value, to maintain the area of the (planar)projection from the first step. This is my personal approach, there are probably many other ways.

Circle from edges SOP, or in an edit state right click and 'make circle'.

https://www.sidefx.com/docs/houdini/nodes/sop/circlefromedges.html [www.sidefx.com]

there is Circle From Edges SOP if helpful (also works on poly or point selections)

or also while in interactive Edit SOP state Shift+C (Make Circle) on selected components

(Circle From Edges) / (Make Circle) has problems on non planar selections (it seems to effect the border only). If you make the selection planar, the result will be better.

Thx everyone for the help

tamte
there is Circle From Edges SOP if helpful (also works on poly or point selections)

or also while in interactive Edit SOP state Shift+C (Make Circle) on selected components

when i use shift-c it reads make circle in the vieuwport but nothing actually circularises.

I can proc the other modes But he make circle mode doesn`t seem 2 work.

Seems to work fine here 19.0.455