Hello,
Since designing and debugging a function blindly is never an easy task I developed 2 “tools” for the Shader editor.
One, WkFunctionDrawer, allows up to 3 functions to be displayed on a graph:
http://werwackfx.com/index.php/graphictools/ue4-main/ue4-articles/35-shaderwkfunctiondrawer
The other, WkDrawValue, displays float values directly as textures:
http://werwackfx.com/index.php/graphictools/ue4-main/ue4-articles/62-shaderwkdrawvalue
I personally use them quite a lot. Hope they can be useful for you too 