Houdini allows 'spare inputs' into a SOP node, which lets you reference extenral data from inside a For-loop.
For an example, I want to scatter some points around the vertices of a grid. I want a random number of points at a random distance from each vertex.
I can create attributes on each vertex to control number of points, radius from vertex and random seed. I can then move that data to the scatter node using Spare Inputs.
Here I have got three wrangles creating data on each vertex on a grid.
f@size = fit01(rand(@ptnum), ch("size_min"), ch("size_max"));
i@number = int(fit01(rand(@ptnum), ch("min"), ch("max")));
f@seed = rand(@ptnum + ch("seed"));
The for loop