I am testing my idea to find the difference between two regions, while one region has discrete sub-regions. I find that RegionUnion and RegionDifference have problems dealing with such problems. I post my script here for a quick check

 `d1 = Disk[{0.5, 0.5}, 0.4];
  d2 = Disk[{1.5, 1.5}, 0.4];
  d3 = Disk[{1.5, 0.5}, 0.4];
  d4 = Disk[{0.5, 1.5}, 0.4];
  u1 = Region[RegionUnion[d1, d2, d3, d4], Axes -> True, 
   AxesOrigin -> {0, 0}]
  u2 = Region[Rectangle[{0, 0}, {2, 2}], Axes -> True, 
   AxesOrigin -> {0, 0}]
  D1 = Region[RegionDifference[u2, u1], Axes -> True, 
   AxesOrigin -> {0, 0}]

I hope to get the region without those four disks in the rectangle. but the code just give the region of the left corner part.

Thanks for any comments.

  • $\begingroup$ Region isn't a valid command. Just do, eg: u1 = RegionUnion[d1, d2, d3, d4], and the RegionPlot[u1]. Also, probably don't want to be using capital D as a variable name. $\endgroup$ Oct 7, 2017 at 7:32
  • $\begingroup$ Thanks. That means Region command is not a command to define a region, and we don't need to define something as region before apply region related commands. Is it right? $\endgroup$ Oct 8, 2017 at 23:36
  • $\begingroup$ Ah, apparently Region is a command. Introduced in v.11, presumably. Sorry, my bad. But yeah, not a command to define a region. $\endgroup$ Oct 8, 2017 at 23:40

1 Answer 1


Only use Region when you want to view the region. The following does what you want:

u1 = RegionUnion[d1, d2, d3, d4];
u2 = Rectangle[{0,0}, {2,2}];
Region @ RegionDifference[u2, u1]

enter image description here


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.