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Unexpected behavior of the procedure `Area` on the object 'Polygon'
The Next CEO of Stack OverflowHow to ContourPlot a Table?Unexpected behavior of Unevaluatedis there a way to construct a pattern that would trigger when an expression is used as a held/unevaluated in some form?How to copy text from InputField without adding spurious spaces?many indefinite integrals do not evaluate in 10.1, looking for the causeWhat is the difference between GenerateDocument and TemplateApply[NotebookTemplate[Comparing exact expressions for equality — is it really OK if I get wrong answer?Simple arithmetic with Irrationals failsFinding area of intersection regionsWhy Area give the wrong results when the region cannot be formed?
$begingroup$
Sometimes get a results, sometimes left unevaluated.
For instance
Area@Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
12
Transpose@(a.b.Transpose[#]) & /@ Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
(a,b - some 2x2 matrices)
Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]
Area@(Transpose@(a.b.Transpose[#]) & /@ Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4] )
Area[Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]]
Area@Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]
(copy and paste)
1440
How to guess when a calculation will give a result and when it will not be evaluated? And why does it not evaluate?
bugs evaluation computational-geometry polygons packed-arrays
edited Mar 22 at 17:18
kirma
10.2k13058
asked Mar 22 at 14:22
Slepecky MamutSlepecky Mamut
635111
$endgroup$
add a comment |
$begingroup$
Sometimes get a results, sometimes left unevaluated.
For instance
Area@Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
12
Transpose@(a.b.Transpose[#]) & /@ Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
(a,b - some 2x2 matrices)
Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]
Area@(Transpose@(a.b.Transpose[#]) & /@ Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4] )
Area[Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]]
Area@Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]
(copy and paste)
1440
How to guess when a calculation will give a result and when it will not be evaluated? And why does it not evaluate?
bugs evaluation computational-geometry polygons packed-arrays
edited Mar 22 at 17:18
kirma
10.2k13058
asked Mar 22 at 14:22
Slepecky MamutSlepecky Mamut
635111
$endgroup$
4
$begingroup$
What are the definitions ofaandb?
$endgroup$
– MarcoB
Mar 22 at 14:36
$begingroup$
If you want to experiment with this and I haven't made a mistake then it looks like hisa.b == 2,7,-16,4This seems to reproduce his results.
$endgroup$
– Bill
Mar 22 at 16:15
add a comment |
$begingroup$
Sometimes get a results, sometimes left unevaluated.
For instance
Area@Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
12
Transpose@(a.b.Transpose[#]) & /@ Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
(a,b - some 2x2 matrices)
Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]
Area@(Transpose@(a.b.Transpose[#]) & /@ Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4] )
Area[Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]]
Area@Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]
(copy and paste)
1440
How to guess when a calculation will give a result and when it will not be evaluated? And why does it not evaluate?
bugs evaluation computational-geometry polygons packed-arrays
edited Mar 22 at 17:18
kirma
10.2k13058
asked Mar 22 at 14:22
Slepecky MamutSlepecky Mamut
635111
$endgroup$
Sometimes get a results, sometimes left unevaluated.
For instance
Area@Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
12
Transpose@(a.b.Transpose[#]) & /@ Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
(a,b - some 2x2 matrices)
Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]
Area@(Transpose@(a.b.Transpose[#]) & /@ Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4] )
Area[Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]]
Area@Polygon[0, 0, 8, -64, 18, -24, 36, -48, 28, 16]
(copy and paste)
1440
How to guess when a calculation will give a result and when it will not be evaluated? And why does it not evaluate?
bugs evaluation computational-geometry polygons packed-arrays
bugs evaluation computational-geometry polygons packed-arrays
edited Mar 22 at 17:18
kirma
10.2k13058
asked Mar 22 at 14:22
Slepecky MamutSlepecky Mamut
635111
edited Mar 22 at 17:18
kirma
10.2k13058
asked Mar 22 at 14:22
Slepecky MamutSlepecky Mamut
635111
edited Mar 22 at 17:18
kirma
10.2k13058
edited Mar 22 at 17:18
kirma
10.2k13058
edited Mar 22 at 17:18
kirma
10.2k13058
10.2k13058
asked Mar 22 at 14:22
Slepecky MamutSlepecky Mamut
635111
asked Mar 22 at 14:22
Slepecky MamutSlepecky Mamut
635111
asked Mar 22 at 14:22
Slepecky MamutSlepecky Mamut
635111
635111
4
$begingroup$
What are the definitions ofaandb?
$endgroup$
– MarcoB
Mar 22 at 14:36
$begingroup$
If you want to experiment with this and I haven't made a mistake then it looks like hisa.b == 2,7,-16,4This seems to reproduce his results.
$endgroup$
– Bill
Mar 22 at 16:15
add a comment |
4
$begingroup$
What are the definitions ofaandb?
$endgroup$
– MarcoB
Mar 22 at 14:36
$begingroup$
If you want to experiment with this and I haven't made a mistake then it looks like hisa.b == 2,7,-16,4This seems to reproduce his results.
$endgroup$
– Bill
Mar 22 at 16:15
4
4
$begingroup$
What are the definitions of
a and b?$endgroup$
– MarcoB
Mar 22 at 14:36
$begingroup$
What are the definitions of
a and b?$endgroup$
– MarcoB
Mar 22 at 14:36
$begingroup$
If you want to experiment with this and I haven't made a mistake then it looks like his
a.b == 2,7,-16,4 This seems to reproduce his results.$endgroup$
– Bill
Mar 22 at 16:15
$begingroup$
If you want to experiment with this and I haven't made a mistake then it looks like his
a.b == 2,7,-16,4 This seems to reproduce his results.$endgroup$
– Bill
Mar 22 at 16:15
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
EDIT: Reported to WRI as CASE:4237867 - and apparently should work on V12. :)
Seems like a bug in my opinion. Consider the following:
With[poly0 = Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4],
With[poly = Transpose[IdentityMatrix[2].Transpose@#] & /@ poly0,
poly0 === poly, Area /@ poly0, poly]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
Although the Mma considers poly0 and its transformed but identical copy (coordinates transformed using IdentityMatrix) identical, they produce different results.
Probably the internal representation of poly is not the same as poly0. At the same time its output form is identical, which actually transforms it to other form if you copy and paste it.
This can be further simplified to show that from the perspective of Polygon two semantically identical coordinate lists can differ:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Area@*Polygon /@ coord0, coord]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
I suspect there's something wrong with the way Polygon reads the internal representation of a list!
EDIT: I think there's a good chance this problem is caused by the fact coord is a packed array, while coord0 is not:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Developer`PackedArrayQ /@ coord0, coord,
Area@*Polygon /@ coord0, Developer`FromPackedArray@coord]]
True, False, True, 12, 12
So, you can use FromPackedArray on the transformed coordinate list as a workaround.
answered Mar 22 at 16:23
kirmakirma
10.2k13058
$endgroup$
add a comment |
$begingroup$
This is a packed array issue:
Area @ Polygon[Developer`ToPackedArray @ 0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
This will be fixed in M12.
answered Mar 22 at 16:49
Carl WollCarl Woll
71.9k395186
$endgroup$
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
EDIT: Reported to WRI as CASE:4237867 - and apparently should work on V12. :)
Seems like a bug in my opinion. Consider the following:
With[poly0 = Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4],
With[poly = Transpose[IdentityMatrix[2].Transpose@#] & /@ poly0,
poly0 === poly, Area /@ poly0, poly]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
Although the Mma considers poly0 and its transformed but identical copy (coordinates transformed using IdentityMatrix) identical, they produce different results.
Probably the internal representation of poly is not the same as poly0. At the same time its output form is identical, which actually transforms it to other form if you copy and paste it.
This can be further simplified to show that from the perspective of Polygon two semantically identical coordinate lists can differ:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Area@*Polygon /@ coord0, coord]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
I suspect there's something wrong with the way Polygon reads the internal representation of a list!
EDIT: I think there's a good chance this problem is caused by the fact coord is a packed array, while coord0 is not:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Developer`PackedArrayQ /@ coord0, coord,
Area@*Polygon /@ coord0, Developer`FromPackedArray@coord]]
True, False, True, 12, 12
So, you can use FromPackedArray on the transformed coordinate list as a workaround.
answered Mar 22 at 16:23
kirmakirma
10.2k13058
$endgroup$
add a comment |
$begingroup$
EDIT: Reported to WRI as CASE:4237867 - and apparently should work on V12. :)
Seems like a bug in my opinion. Consider the following:
With[poly0 = Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4],
With[poly = Transpose[IdentityMatrix[2].Transpose@#] & /@ poly0,
poly0 === poly, Area /@ poly0, poly]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
Although the Mma considers poly0 and its transformed but identical copy (coordinates transformed using IdentityMatrix) identical, they produce different results.
Probably the internal representation of poly is not the same as poly0. At the same time its output form is identical, which actually transforms it to other form if you copy and paste it.
This can be further simplified to show that from the perspective of Polygon two semantically identical coordinate lists can differ:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Area@*Polygon /@ coord0, coord]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
I suspect there's something wrong with the way Polygon reads the internal representation of a list!
EDIT: I think there's a good chance this problem is caused by the fact coord is a packed array, while coord0 is not:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Developer`PackedArrayQ /@ coord0, coord,
Area@*Polygon /@ coord0, Developer`FromPackedArray@coord]]
True, False, True, 12, 12
So, you can use FromPackedArray on the transformed coordinate list as a workaround.
answered Mar 22 at 16:23
kirmakirma
10.2k13058
$endgroup$
add a comment |
$begingroup$
EDIT: Reported to WRI as CASE:4237867 - and apparently should work on V12. :)
Seems like a bug in my opinion. Consider the following:
With[poly0 = Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4],
With[poly = Transpose[IdentityMatrix[2].Transpose@#] & /@ poly0,
poly0 === poly, Area /@ poly0, poly]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
Although the Mma considers poly0 and its transformed but identical copy (coordinates transformed using IdentityMatrix) identical, they produce different results.
Probably the internal representation of poly is not the same as poly0. At the same time its output form is identical, which actually transforms it to other form if you copy and paste it.
This can be further simplified to show that from the perspective of Polygon two semantically identical coordinate lists can differ:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Area@*Polygon /@ coord0, coord]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
I suspect there's something wrong with the way Polygon reads the internal representation of a list!
EDIT: I think there's a good chance this problem is caused by the fact coord is a packed array, while coord0 is not:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Developer`PackedArrayQ /@ coord0, coord,
Area@*Polygon /@ coord0, Developer`FromPackedArray@coord]]
True, False, True, 12, 12
So, you can use FromPackedArray on the transformed coordinate list as a workaround.
answered Mar 22 at 16:23
kirmakirma
10.2k13058
$endgroup$
EDIT: Reported to WRI as CASE:4237867 - and apparently should work on V12. :)
Seems like a bug in my opinion. Consider the following:
With[poly0 = Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4],
With[poly = Transpose[IdentityMatrix[2].Transpose@#] & /@ poly0,
poly0 === poly, Area /@ poly0, poly]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
Although the Mma considers poly0 and its transformed but identical copy (coordinates transformed using IdentityMatrix) identical, they produce different results.
Probably the internal representation of poly is not the same as poly0. At the same time its output form is identical, which actually transforms it to other form if you copy and paste it.
This can be further simplified to show that from the perspective of Polygon two semantically identical coordinate lists can differ:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Area@*Polygon /@ coord0, coord]]
True, 12, Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
I suspect there's something wrong with the way Polygon reads the internal representation of a list!
EDIT: I think there's a good chance this problem is caused by the fact coord is a packed array, while coord0 is not:
With[coord0 = 0, 0, 4, 0, 2, 2, 4, 4, 0, 4,
With[coord = Transpose[IdentityMatrix[2].Transpose@coord0],
coord0 === coord, Developer`PackedArrayQ /@ coord0, coord,
Area@*Polygon /@ coord0, Developer`FromPackedArray@coord]]
True, False, True, 12, 12
So, you can use FromPackedArray on the transformed coordinate list as a workaround.
answered Mar 22 at 16:23
kirmakirma
10.2k13058
edited Mar 22 at 17:02
answered Mar 22 at 16:23
kirmakirma
10.2k13058
answered Mar 22 at 16:23
kirmakirma
10.2k13058
answered Mar 22 at 16:23
kirmakirma
10.2k13058
10.2k13058
add a comment |
add a comment |
$begingroup$
This is a packed array issue:
Area @ Polygon[Developer`ToPackedArray @ 0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
This will be fixed in M12.
answered Mar 22 at 16:49
Carl WollCarl Woll
71.9k395186
$endgroup$
add a comment |
$begingroup$
This is a packed array issue:
Area @ Polygon[Developer`ToPackedArray @ 0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
This will be fixed in M12.
answered Mar 22 at 16:49
Carl WollCarl Woll
71.9k395186
$endgroup$
add a comment |
$begingroup$
This is a packed array issue:
Area @ Polygon[Developer`ToPackedArray @ 0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
This will be fixed in M12.
answered Mar 22 at 16:49
Carl WollCarl Woll
71.9k395186
$endgroup$
This is a packed array issue:
Area @ Polygon[Developer`ToPackedArray @ 0, 0, 4, 0, 2, 2, 4, 4, 0, 4]
Area[Polygon[0, 0, 4, 0, 2, 2, 4, 4, 0, 4]]
This will be fixed in M12.
answered Mar 22 at 16:49
Carl WollCarl Woll
71.9k395186
answered Mar 22 at 16:49
Carl WollCarl Woll
71.9k395186
answered Mar 22 at 16:49
Carl WollCarl Woll
71.9k395186
answered Mar 22 at 16:49
Carl WollCarl Woll
71.9k395186
71.9k395186
add a comment |
add a comment |
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4
$begingroup$
What are the definitions of
aandb?$endgroup$
– MarcoB
Mar 22 at 14:36
$begingroup$
If you want to experiment with this and I haven't made a mistake then it looks like his
a.b == 2,7,-16,4This seems to reproduce his results.$endgroup$
– Bill
Mar 22 at 16:15