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I have a simple question I have no answer to - how do I create an Epilog in (for example) a DensityPlot that consists of a Disk[] with a hole with the inner radius being r1 and the outer radius being r2? Imagine something like this:

Graphics[{{Gray, Disk[{0, 0}, 1]}, {White, Disk[{0, 0}, 0.5]}}]

However, this would hide the density plot in the "hole" (it would stay white). How to create such object as an epilog to a density plot, stream plot etc?

I had two ideas: first, if there is something like GraphicsDifference, that would be it: bigger Disk minus the smaller one creates the object I'm after. However, I found no such function.

Second: create a circle using a really thick line so that the inner boundary corresponds to r1 and the outer to r2. However this would not scale nicely (i.e. using ImageSize -> ... during export would not preserve these radii).

Thanks.

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  • 4
    $\begingroup$ Annulus was introduced in 10.2 $\endgroup$ – Kuba May 9 '18 at 20:32
  • $\begingroup$ Thanks, that's great! Exactly what I was looking for! I googled a lot of queries like "Disk with a hole", but nothing returned Annulus...I am sorry though. Just curious: how would you make a graphics with rectangular hole so that the hole is transparent (the plot is visible through it)? So as to keep to the spirit of the original question... $\endgroup$ – user16320 May 9 '18 at 20:36
  • $\begingroup$ A disk with a rectangular hole or a rectangle? $\endgroup$ – Kuba May 9 '18 at 20:46
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use region tools to construct more general figures (addressing comment):

r = RegionDifference[ Disk[{8, 8}, 2], Rectangle[{7, 7}, {9, 8}]];
Show[
 ContourPlot[Cos[x] + Cos[y], {x, 0, 4 Pi}, {y, 0, 4 Pi}], 
 RegionPlot[r, Frame -> False, PlotStyle -> Red, 
  BoundaryStyle -> Black]]

or

ContourPlot[Cos[x] + Cos[y], {x, 0, 4 Pi}, {y, 0, 4 Pi}, 
 Epilog -> 
  First@RegionPlot[r, Frame -> False, PlotStyle -> Red, 
    BoundaryStyle -> Black]]

enter image description here

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  • $\begingroup$ This is what I've been looking for! Thank you. $\endgroup$ – user16320 May 9 '18 at 22:20

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