Inspect math function results on XY chart. Tool designed for procedural textures creating purpose, ofc use it for any purpose.
HOW TO: 1) 3D Viewport switch to Rendered shading mode, 2) In Node Editor in "Test Field" frame manipulate the X value by plugging any nodes you like (math node, mix rgb, etc.) and see results in the viewport, 3) Set curves color/thickness.
Included 3 setups (see Material tab): 1 Curve, 2 Curves, RGB Curves example.