So far we have explored many interesting aspects and applications of D3 force layout; however, in all of these prior recipes we simply apply force layout's computation (gravity, charge, friction, and momentum) directly to our visualization. In this recipe we will go one step further to implement custom force manipulation, hence creating our own type of force.
In this recipe we will first generate five sets of colored particles then we assign corresponding colors and categorical force pull to user's touch, hence pulling only the particles that match the color. Since this recipe is a bit complex, I will give an example here: if I touch the visualization with my first finger it will generate a blue circle and pull all blue particles to that circle, while my second touch will generate an orange circle and only pull the orange particles. This type of force manipulation is commonly referred to as categorical multi-foci.
