Collision filtering on Box2D

Hello,
I’m trying to find the way to tell a group of circles not to collide each other on Box2D.
This is how I’m creating the object, I started testing isSleeping() but it is not really the solution.

ofVec2f attractor = ofVec2f(charPoints[j].x+center.x,charPoints[j].y+center.y);
shared_ptr<ofxBox2dCircle> circle = shared_ptr<ofxBox2dCircle>(new ofxBox2dCircle);
circle.get()->setPhysics(2.0, 3.0, 0.9);
circle.get()->setup(box2d.getWorld(), attractor.x, attractor.y, 3);
circle.get()->isSleeping();
circles.push_back(circle);
coordinates.push_back(attractor);

Any suggestion?
Thanks

Solution