i have made an interface from Radio Button type folders and I want to use it in Switch SOP to switch between the inputs.
How can i access the information about active radio button by expression?
Or is there some other way of using Radio Buttons?

I'm actually curious about this too.

Like this?

The folder set is named “folders”. To access it with an expression you need to access the first element in the set, so ch(“../folders1”).

This method works for any type of folders, not just Radio buttons.

Graham,
I've tried your solution on a Digital Asset but it does not seem to recognize the folder name. No matter what I do Houdini transform the name of the folder adding a number when placing the asset onto the scene, and I am pretty sure the name is original.

Necro thread... the answer is: you need to set the channel reference to the name of the second folder.

Folder Name

folders,folders_1,folders_2 ......

Accessing to the flag

ch("../folders1")

I don't know why.....this is not in the docs.