RegionPlot of annulus gives a mesh












1












$begingroup$


So I tried plotting an annulus in two ways:



RegionPlot[Annulus[{0,0},{a,b}]]

Graphics[Annulus[{0,0},{a,b}]]


Why does RegionPlot give a fractal looking thing? (see below for when a=1; b=5;)
RegionPlot image



*note, I used wolfram programing lab.






graphics regions







share|improve this question











$endgroup$












  • $begingroup$
    What are $a$ and $b$ here?
    $endgroup$
    – mjw
    Mar 29 at 20:03










  • $begingroup$
    Try a=1; b=5; But really any values give something weird
    $endgroup$
    – Ion Sme
    Mar 29 at 20:08






  • 4




    $begingroup$
    Because it discretized the region in order to plot it, and it is showing the underlying triangulation mesh.
    $endgroup$
    – MarcoB
    Mar 29 at 20:12






  • 1




    $begingroup$
    @IonSme I guess they just use different defaults for plotting; the Graphics result is "normal-looking" though.
    $endgroup$
    – MarcoB
    Mar 29 at 20:17






  • 2




    $begingroup$
    There are some subtle differences going on how Mma shows Regions and RegionPlot Graphics. Also Regions can be defined analytically via ImplicitRegion or ParametricRegion or as 'flat' MeshRegions. DiscretizeRegion converts every type to a MeshRegion and some functions like RegionPlot might use something similar to DiscretizeRegion under the hood to make plotting easier, whose discretization it for some reason decides to show. Like others wrote you can use ImplicitRegion to get a different (not discretized) look in your case.
    $endgroup$
    – Thies Heidecke
    Mar 29 at 21:19


















1












$begingroup$


So I tried plotting an annulus in two ways:



RegionPlot[Annulus[{0,0},{a,b}]]

Graphics[Annulus[{0,0},{a,b}]]


Why does RegionPlot give a fractal looking thing? (see below for when a=1; b=5;)
RegionPlot image



*note, I used wolfram programing lab.






graphics regions







share|improve this question











$endgroup$












  • $begingroup$
    What are $a$ and $b$ here?
    $endgroup$
    – mjw
    Mar 29 at 20:03










  • $begingroup$
    Try a=1; b=5; But really any values give something weird
    $endgroup$
    – Ion Sme
    Mar 29 at 20:08






  • 4




    $begingroup$
    Because it discretized the region in order to plot it, and it is showing the underlying triangulation mesh.
    $endgroup$
    – MarcoB
    Mar 29 at 20:12






  • 1




    $begingroup$
    @IonSme I guess they just use different defaults for plotting; the Graphics result is "normal-looking" though.
    $endgroup$
    – MarcoB
    Mar 29 at 20:17






  • 2




    $begingroup$
    There are some subtle differences going on how Mma shows Regions and RegionPlot Graphics. Also Regions can be defined analytically via ImplicitRegion or ParametricRegion or as 'flat' MeshRegions. DiscretizeRegion converts every type to a MeshRegion and some functions like RegionPlot might use something similar to DiscretizeRegion under the hood to make plotting easier, whose discretization it for some reason decides to show. Like others wrote you can use ImplicitRegion to get a different (not discretized) look in your case.
    $endgroup$
    – Thies Heidecke
    Mar 29 at 21:19
















1












1








1





$begingroup$


So I tried plotting an annulus in two ways:



RegionPlot[Annulus[{0,0},{a,b}]]

Graphics[Annulus[{0,0},{a,b}]]


Why does RegionPlot give a fractal looking thing? (see below for when a=1; b=5;)
RegionPlot image



*note, I used wolfram programing lab.






graphics regions







share|improve this question











$endgroup$




So I tried plotting an annulus in two ways:



RegionPlot[Annulus[{0,0},{a,b}]]

Graphics[Annulus[{0,0},{a,b}]]


Why does RegionPlot give a fractal looking thing? (see below for when a=1; b=5;)
RegionPlot image



*note, I used wolfram programing lab.






graphics regions




graphics regions






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Mar 29 at 20:48









MarcoB

38.4k556115




38.4k556115










asked Mar 29 at 20:00









Ion SmeIon Sme

877




877












  • $begingroup$
    What are $a$ and $b$ here?
    $endgroup$
    – mjw
    Mar 29 at 20:03










  • $begingroup$
    Try a=1; b=5; But really any values give something weird
    $endgroup$
    – Ion Sme
    Mar 29 at 20:08






  • 4




    $begingroup$
    Because it discretized the region in order to plot it, and it is showing the underlying triangulation mesh.
    $endgroup$
    – MarcoB
    Mar 29 at 20:12






  • 1




    $begingroup$
    @IonSme I guess they just use different defaults for plotting; the Graphics result is "normal-looking" though.
    $endgroup$
    – MarcoB
    Mar 29 at 20:17






  • 2




    $begingroup$
    There are some subtle differences going on how Mma shows Regions and RegionPlot Graphics. Also Regions can be defined analytically via ImplicitRegion or ParametricRegion or as 'flat' MeshRegions. DiscretizeRegion converts every type to a MeshRegion and some functions like RegionPlot might use something similar to DiscretizeRegion under the hood to make plotting easier, whose discretization it for some reason decides to show. Like others wrote you can use ImplicitRegion to get a different (not discretized) look in your case.
    $endgroup$
    – Thies Heidecke
    Mar 29 at 21:19




















  • $begingroup$
    What are $a$ and $b$ here?
    $endgroup$
    – mjw
    Mar 29 at 20:03










  • $begingroup$
    Try a=1; b=5; But really any values give something weird
    $endgroup$
    – Ion Sme
    Mar 29 at 20:08






  • 4




    $begingroup$
    Because it discretized the region in order to plot it, and it is showing the underlying triangulation mesh.
    $endgroup$
    – MarcoB
    Mar 29 at 20:12






  • 1




    $begingroup$
    @IonSme I guess they just use different defaults for plotting; the Graphics result is "normal-looking" though.
    $endgroup$
    – MarcoB
    Mar 29 at 20:17






  • 2




    $begingroup$
    There are some subtle differences going on how Mma shows Regions and RegionPlot Graphics. Also Regions can be defined analytically via ImplicitRegion or ParametricRegion or as 'flat' MeshRegions. DiscretizeRegion converts every type to a MeshRegion and some functions like RegionPlot might use something similar to DiscretizeRegion under the hood to make plotting easier, whose discretization it for some reason decides to show. Like others wrote you can use ImplicitRegion to get a different (not discretized) look in your case.
    $endgroup$
    – Thies Heidecke
    Mar 29 at 21:19


















$begingroup$
What are $a$ and $b$ here?
$endgroup$
– mjw
Mar 29 at 20:03




$begingroup$
What are $a$ and $b$ here?
$endgroup$
– mjw
Mar 29 at 20:03












$begingroup$
Try a=1; b=5; But really any values give something weird
$endgroup$
– Ion Sme
Mar 29 at 20:08




$begingroup$
Try a=1; b=5; But really any values give something weird
$endgroup$
– Ion Sme
Mar 29 at 20:08




4




4




$begingroup$
Because it discretized the region in order to plot it, and it is showing the underlying triangulation mesh.
$endgroup$
– MarcoB
Mar 29 at 20:12




$begingroup$
Because it discretized the region in order to plot it, and it is showing the underlying triangulation mesh.
$endgroup$
– MarcoB
Mar 29 at 20:12




1




1




$begingroup$
@IonSme I guess they just use different defaults for plotting; the Graphics result is "normal-looking" though.
$endgroup$
– MarcoB
Mar 29 at 20:17




$begingroup$
@IonSme I guess they just use different defaults for plotting; the Graphics result is "normal-looking" though.
$endgroup$
– MarcoB
Mar 29 at 20:17




2




2




$begingroup$
There are some subtle differences going on how Mma shows Regions and RegionPlot Graphics. Also Regions can be defined analytically via ImplicitRegion or ParametricRegion or as 'flat' MeshRegions. DiscretizeRegion converts every type to a MeshRegion and some functions like RegionPlot might use something similar to DiscretizeRegion under the hood to make plotting easier, whose discretization it for some reason decides to show. Like others wrote you can use ImplicitRegion to get a different (not discretized) look in your case.
$endgroup$
– Thies Heidecke
Mar 29 at 21:19






$begingroup$
There are some subtle differences going on how Mma shows Regions and RegionPlot Graphics. Also Regions can be defined analytically via ImplicitRegion or ParametricRegion or as 'flat' MeshRegions. DiscretizeRegion converts every type to a MeshRegion and some functions like RegionPlot might use something similar to DiscretizeRegion under the hood to make plotting easier, whose discretization it for some reason decides to show. Like others wrote you can use ImplicitRegion to get a different (not discretized) look in your case.
$endgroup$
– Thies Heidecke
Mar 29 at 21:19












1 Answer
1






active

oldest

votes


















4












$begingroup$

 a = 1; b = 5;


Please try plotting with Region. These look okay to me:



 Region[RegionDifference[Disk[{0, 0}, b], Disk[{0, 0}, a]]]


enter image description here



 Region[Annulus[{0, 0}, {a, b}]]


enter image description here



Here is a decent plot, with RegionPlot:



 RegionPlot[x^2 + y^2 > 1 && x^2 + y^2 < 25, {x, -6, 6}, {y, -6, 6}]


enter image description here



Here it is (again) with Graphics:



 Graphics[{LightBlue, Annulus[{0, 0}, {a, b}]}]


enter image description here






share|improve this answer











$endgroup$













  • $begingroup$
    Hmmm, that worked, but why is RegionPlot so funky?
    $endgroup$
    – Ion Sme
    Mar 29 at 20:13






  • 1




    $begingroup$
    I think MarcoB mostly answers this below your question. So we can then ask: Why does RegionPlot use one algorithm, and Region another? RegionPlot seems to like functions as inputs, and also likes to have the $x$ and $y$ ranges speciifed ...
    $endgroup$
    – mjw
    Mar 29 at 20:17












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1 Answer
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1 Answer
1






active

oldest

votes









active

oldest

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active

oldest

votes









4












$begingroup$

 a = 1; b = 5;


Please try plotting with Region. These look okay to me:



 Region[RegionDifference[Disk[{0, 0}, b], Disk[{0, 0}, a]]]


enter image description here



 Region[Annulus[{0, 0}, {a, b}]]


enter image description here



Here is a decent plot, with RegionPlot:



 RegionPlot[x^2 + y^2 > 1 && x^2 + y^2 < 25, {x, -6, 6}, {y, -6, 6}]


enter image description here



Here it is (again) with Graphics:



 Graphics[{LightBlue, Annulus[{0, 0}, {a, b}]}]


enter image description here






share|improve this answer











$endgroup$













  • $begingroup$
    Hmmm, that worked, but why is RegionPlot so funky?
    $endgroup$
    – Ion Sme
    Mar 29 at 20:13






  • 1




    $begingroup$
    I think MarcoB mostly answers this below your question. So we can then ask: Why does RegionPlot use one algorithm, and Region another? RegionPlot seems to like functions as inputs, and also likes to have the $x$ and $y$ ranges speciifed ...
    $endgroup$
    – mjw
    Mar 29 at 20:17
















4












$begingroup$

 a = 1; b = 5;


Please try plotting with Region. These look okay to me:



 Region[RegionDifference[Disk[{0, 0}, b], Disk[{0, 0}, a]]]


enter image description here



 Region[Annulus[{0, 0}, {a, b}]]


enter image description here



Here is a decent plot, with RegionPlot:



 RegionPlot[x^2 + y^2 > 1 && x^2 + y^2 < 25, {x, -6, 6}, {y, -6, 6}]


enter image description here



Here it is (again) with Graphics:



 Graphics[{LightBlue, Annulus[{0, 0}, {a, b}]}]


enter image description here






share|improve this answer











$endgroup$













  • $begingroup$
    Hmmm, that worked, but why is RegionPlot so funky?
    $endgroup$
    – Ion Sme
    Mar 29 at 20:13






  • 1




    $begingroup$
    I think MarcoB mostly answers this below your question. So we can then ask: Why does RegionPlot use one algorithm, and Region another? RegionPlot seems to like functions as inputs, and also likes to have the $x$ and $y$ ranges speciifed ...
    $endgroup$
    – mjw
    Mar 29 at 20:17














4












4








4





$begingroup$

 a = 1; b = 5;


Please try plotting with Region. These look okay to me:



 Region[RegionDifference[Disk[{0, 0}, b], Disk[{0, 0}, a]]]


enter image description here



 Region[Annulus[{0, 0}, {a, b}]]


enter image description here



Here is a decent plot, with RegionPlot:



 RegionPlot[x^2 + y^2 > 1 && x^2 + y^2 < 25, {x, -6, 6}, {y, -6, 6}]


enter image description here



Here it is (again) with Graphics:



 Graphics[{LightBlue, Annulus[{0, 0}, {a, b}]}]


enter image description here






share|improve this answer











$endgroup$



 a = 1; b = 5;


Please try plotting with Region. These look okay to me:



 Region[RegionDifference[Disk[{0, 0}, b], Disk[{0, 0}, a]]]


enter image description here



 Region[Annulus[{0, 0}, {a, b}]]


enter image description here



Here is a decent plot, with RegionPlot:



 RegionPlot[x^2 + y^2 > 1 && x^2 + y^2 < 25, {x, -6, 6}, {y, -6, 6}]


enter image description here



Here it is (again) with Graphics:



 Graphics[{LightBlue, Annulus[{0, 0}, {a, b}]}]


enter image description here







share|improve this answer














share|improve this answer



share|improve this answer








edited Mar 29 at 20:26

























answered Mar 29 at 20:07









mjwmjw

1,24210




1,24210












  • $begingroup$
    Hmmm, that worked, but why is RegionPlot so funky?
    $endgroup$
    – Ion Sme
    Mar 29 at 20:13






  • 1




    $begingroup$
    I think MarcoB mostly answers this below your question. So we can then ask: Why does RegionPlot use one algorithm, and Region another? RegionPlot seems to like functions as inputs, and also likes to have the $x$ and $y$ ranges speciifed ...
    $endgroup$
    – mjw
    Mar 29 at 20:17


















  • $begingroup$
    Hmmm, that worked, but why is RegionPlot so funky?
    $endgroup$
    – Ion Sme
    Mar 29 at 20:13






  • 1




    $begingroup$
    I think MarcoB mostly answers this below your question. So we can then ask: Why does RegionPlot use one algorithm, and Region another? RegionPlot seems to like functions as inputs, and also likes to have the $x$ and $y$ ranges speciifed ...
    $endgroup$
    – mjw
    Mar 29 at 20:17
















$begingroup$
Hmmm, that worked, but why is RegionPlot so funky?
$endgroup$
– Ion Sme
Mar 29 at 20:13




$begingroup$
Hmmm, that worked, but why is RegionPlot so funky?
$endgroup$
– Ion Sme
Mar 29 at 20:13




1




1




$begingroup$
I think MarcoB mostly answers this below your question. So we can then ask: Why does RegionPlot use one algorithm, and Region another? RegionPlot seems to like functions as inputs, and also likes to have the $x$ and $y$ ranges speciifed ...
$endgroup$
– mjw
Mar 29 at 20:17




$begingroup$
I think MarcoB mostly answers this below your question. So we can then ask: Why does RegionPlot use one algorithm, and Region another? RegionPlot seems to like functions as inputs, and also likes to have the $x$ and $y$ ranges speciifed ...
$endgroup$
– mjw
Mar 29 at 20:17


















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