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In this very simple example a region consisting of two lines forming a right angle is defined as

reg = ImplicitRegion[(1 <= r < 3 && z == 0) || (r == 3 &&0 <= z <= 2), {z, r}];

but

RegionPlot[reg ]

enter image description here

only shows vertical part of it.

I tried PlotRange, PlotPoints without success and checked

RegionMember[reg, {1, 3}] (* True*)

How to show the complete region? Thanks!

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  • $\begingroup$ PlotRange->{{-1,10},{-1,10}} ? $\endgroup$
    – rhermans
    Commented Jul 8, 2022 at 13:48
  • 1
    $\begingroup$ Thanks, no effect in Mathematica v12.2 $\endgroup$
    – Ulrich Neumann
    Commented Jul 8, 2022 at 13:53

2 Answers 2

Reset to default
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This seems to work in V12.2 (Mac). It does what seems obivous and is probably done in V13 (discretize each component represented by the arguments to Or):

RegionPlot[
 List @@ Thread[reg, Or] // Map@DiscretizeRegion // RegionUnion // 
  Evaluate]
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  • $\begingroup$ Really clever, thank you very much! $\endgroup$
    – Ulrich Neumann
    Commented Jul 10, 2022 at 16:10
1
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$Version
(* 13.1.0 for Microsoft Windows (64-bit) (June 16, 2022) *)

RegionPlot not always automatic discretize the region.

DiscretizeRegion[reg, {{-10, 10}, {-10, 10}}]
RegionPlot[%]

enter image description here

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1
  • $\begingroup$ Thanks! In v12.2 your solution doesn't work unfortunately. What's your Mathematica version? $\endgroup$
    – Ulrich Neumann
    Commented Jul 8, 2022 at 13:29

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