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I have a function $Z(r, \theta)$ that I would like to plot over the unit disk. I could of course plot it as $Z(\sqrt{x^2+y^2}, \arctan(y/x))$, but the best I can do with this is a square plot. I would like a plot defined from $0<R<1$ and $0<\theta<2\pi$, such that it looks something like the plots shown here:

Zernike polynomial plots

How can I make Mathematica generate a plot like this? Thank you!

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  • $\begingroup$ You might be interested in RegionFunction. $\endgroup$ – J. M. will be back soon♦ Nov 24 '15 at 6:07
  • $\begingroup$ Ah that works perfectly - thank you!! Though I do wonder if Mathematica has something more intuitive built in, as it seems like a common enough application. $\endgroup$ – Bslugger360 Nov 24 '15 at 6:10
  • $\begingroup$ Just to be clear, I'm still leaving this open for a solution as this method doesn't quite work - using $\arctan(y/x)$ causes discontinuities at x=0 that mess up the way the plot comes out. $\endgroup$ – Bslugger360 Nov 24 '15 at 6:34
  • $\begingroup$ That's because you have to use two-argument arctangent (ArcTan[x, y]) for the purpose. $\endgroup$ – J. M. will be back soon♦ Nov 24 '15 at 6:39
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Here's my attempt to plot the Zernike functions on the unit disk:

ZernikeZ[n_Integer, m_Integer, r_, θ_] /; -n <= m <= n := 
         If[m < 0, Sin[m θ], Cos[m θ]] ZernikeR[n, m, r]

Table[DensityPlot[ZernikeZ[n, m, Norm[{x, y}], ArcTan[x, y]], {x, y} ∈ Disk[],
                  ColorFunction -> (ColorData[{"ThermometerColors",  "Reverse"},
                                              LogisticSigmoid[2 #]] &), 
                  ColorFunctionScaling -> False, Frame -> False, 
                  PlotPoints -> 55],
      {n, 0, 4}, {m, -n, n, 2}] // GraphicsGrid

Zernike on a disk

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  • $\begingroup$ (Older versions of Mathematica can use RegionFunction instead.) $\endgroup$ – J. M. will be back soon♦ Nov 24 '15 at 6:44
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    $\begingroup$ Much older ones ... v9 accepts Disk[ ] $\endgroup$ – Dr. belisarius Nov 24 '15 at 6:46
  • $\begingroup$ Is the LogisticSigmoid[ ] in there for pure Fermi love, or is something really useful? $\endgroup$ – Dr. belisarius Nov 24 '15 at 6:47
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    $\begingroup$ @bel, it allows me to map $(-\infty,\infty)$ to $(0,1)$, with $0$ being the white(-ish) color, and positive and negative values mapped to the extreme colors. I've used this rescaling before on this site... $\endgroup$ – J. M. will be back soon♦ Nov 24 '15 at 6:49
  • $\begingroup$ Ah, OK.nice one.Don't remember seeing it used like this before, but the German doctor is always mumbling in my ear trying to distract me, so ... $\endgroup$ – Dr. belisarius Nov 24 '15 at 6:51

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