The 2D function f(r,φ) = sin(12πr);, colored 2D representation. Low function values are colored blue, high ones red.
<a href="//commons.wikimedia.org/wiki/User:Roderich_Kahn" title="User:Roderich Kahn">Roderich Kahn</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>