Questions tagged [regions]

Questions about functionality that defines or operates on regions (i.e., an open, connected set), including geometric, mesh-based, or data and formula-defined regions.

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3
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3answers
222 views

Using the Disk graphics primitive

Please be kind enough to give me some indication on how to use the Disk graphics primitive in any of these cases: I want to calculate the area and perimeter of the ...
0
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1answer
58 views

BoundaryDiscretizeRegion Plots does not work with ParametricPlot3D

I am trying wit this data ...
0
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0answers
15 views

Creating a region for Plot3D by using an interpolating function as limit

I have a function sigma[qr,q0] of two variables with a sharp delta-like peak that cannot be numerically integrated by NIntegrate, like this: Since the upper and lower regions excluding the peak are ...
1
vote
1answer
51 views

Blunt edges of an octahedron by Region

Why does the octahedron constructed by the following code have blunt edges ? Region[ImplicitRegion[Abs[x] + Abs[y] + Abs[z] <= 1, {x, y, z}]] How to improve it?...
3
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0answers
54 views

Surface area of a cube

When I try to compute the surface area of a simple cube it appears to give me the surface area of one of its faces, not the whole cube: ...
2
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2answers
118 views

How to extrude a planar mesh to a volume slice?

Is there an easy way to extrude a planar 2D-mesh to a volume slice? ring = RegionDifference[Disk[{0, 0}, 1], Disk[{0, 0}, 1/2]]; DiscretizeRegion[ring] The ...
4
votes
1answer
50 views

Get minimum y of a certain x in a region

I have a region and a number x, and I would like to get the minimum y such that (x, y) is on the edge of the region. How can I do this? For example, if I have the region ...
0
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0answers
25 views

Getting error message RegionPlot3D::boolf

I want to visualize the bounded region for a linear programming problem. I used the folowwing, however it gives me an error : ...
0
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0answers
26 views

RegionIntersection of two Line-objects

Looking for the intersection of two "boundary meshregions" ...
3
votes
1answer
65 views

RegionUnion works but RegionIntersection does not

I am trying to create an Alberti's window figure as described in this question, in which a (three-dimensional) polyhedron (e.g., dodecahedron) is projected onto a (two-dimensional) plane. I realized ...
1
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0answers
40 views

Combining MeshRegions of generated 3D shapes and RandomPolygons

I am interested in generating 3D a joint BoundaryMeshRegion or a MeshRegion from different shapes and polygons. This works for <...
1
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0answers
29 views

RegionPlot of a ParametricRegion (problems MMA v11.0.1)

Having problems to visualize a ParametricRegion I took an example from the documentation ...
3
votes
2answers
123 views

Automatically bound histogram regions?

Given a histogram of some data, such as e.g. in the following sample https://www.codepile.net/pile/NLlNgP60 ...
2
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2answers
153 views

Getting an Accurate Transformed Region (Part II)

I asked earlier about transforming a set of curves and getting an accurate plot when a curve goes to infinity: Getting an Accurate Transformed Region Here is an example where a transformed region ...
1
vote
1answer
101 views

Getting an Accurate Transformed Region

I would like to get an accurate plot of the image of concentric circles under the transformation $$f(z) = \log(1+z).$$ I've defined $\cal R$ as the union of a few circles: ...
0
votes
0answers
41 views

Discrete Sum of Function over a Region

I might have completely missed something in my search. I want to discretely sum over a function, $f(x_i,y_j)$ multiplied by some other function $g$ over a general region $S$. $$\sum_{(x,y)\in S}f(x,...
1
vote
1answer
133 views

Discretization and Dirac Delta function

Consider the following integral: \begin{align} I= \int_{\mathbb{R}^9}\frac{d^3\mathbf{x_1}\,d^3\mathbf{x_2}\,d^3\mathbf{x_3}}{|\mathbf{x}_1|\sqrt{|\mathbf{x}_2||\mathbf{x}_3|}}f(\mathbf{x_2})f(\mathbf{...
6
votes
2answers
90 views

How to refine a linear FEM mesh in three regions?

I am trying to solve the one-dimensional wave equation with a frequency dependent source function over three intervals with varying velocity. I need to refine the mesh over the low velocity regions ...
0
votes
0answers
22 views

Unitary group as a region

I would like to compute the area of some subspaces of $SU(n)^d$ defined by group equation (basically $U_{i_1}^{e_1}\dots U_{i_k}^{e_k}=1$) . I know that there is the function ...
0
votes
0answers
30 views

TransformedRegion with Circular Sectors

Here is a circular sector: Disk[{0, 0}, 1, {-\[Pi]/6, \[Pi]/6}] I'd like to reflect that about a vertical line. I could use ...
0
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1answer
28 views

RegionPlot avoiding some complex terms

I have a system of inequalities given as follows: ...
0
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0answers
27 views

What is better here, PlotPoints or MaxRecursion?

I have some function f[x,y], with x ranging from 0.5 to 62.5 and y ranging from 10^-20 to 10^-5. Near x = 62 the function starts to increase very fast and takes at x = 62.5 some large finite value. I ...
7
votes
2answers
100 views

Discretisation of region intersection in 3D

If I try to discretise the intersection (BoundaryDiscretizeRegion), of a shell in a cuboid, some of the regions (that are found with RegionIntersection) are lost in the discretising process. I tried ...
0
votes
1answer
25 views

Inconsistent region plot?

If I do a region plot of the following inequality, ...
4
votes
2answers
106 views

Automatic solution to label boundary elements with BoundaryMarkerFunction

Preparations Mathematica 11.3, Windows. Let us say I have a rectangular region with 10 little holes inside. Their coordinates are given by positionList. The ...
1
vote
1answer
40 views

Integrating in regions

I have three rectangles of the same size: ...
2
votes
1answer
52 views

Combine regions?

I can do: Region[Line[{{0, 0}, {1, 0}}]] And I can do: Region[Circle[{1, 0.5`}, 0.5`, {-90 \[Degree], 90 \[Degree]}]] Can ...
3
votes
0answers
45 views

Regions and their combinations

I met stupid problems playing with combinations of simple 3D regions. Can anyboby explain what is wrong in my code? I need to make a model for 3D-printing. ...
2
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0answers
42 views

Encoding spatial data in Mathematica

I am doing some experimentation with machine learning and robotics, and want Mathematica to be my primary platform. For it, I need to represent a room with some obstacles (circles) and a goal (square)....
1
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0answers
30 views

Combining several geometric regions by adding pointwise?

Given two regions $D_1, D_2 \subseteq \mathbb{R}^2$, I'm looking to combine them by adding pointwise: $$D_1 + D_2 := \left\{ (a+x, b+y) \mid (a,b) \in D_1, (x,y) \in D_2 \right\}.$$ Even more ...
0
votes
2answers
60 views

Plot region in between two discrete functions

I am trying to plot the region in between two curves that I only have as discrete data, without plotting the curves corresponding to the data. In principle, I could interpolate the functions and then ...
0
votes
0answers
22 views

Finding nonzero points in a wide multidimensional space (but bounded)

I have a quite complicated region over 5D, and I want to know whether it is nonzero over a given interval. I don't even need to know the points (although it would be nice), but I would need to know ...
1
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0answers
37 views

Possible bug with InnerPolygon and RegionUnion in version 12

case1 case2 case3 ...
1
vote
1answer
111 views

Unable to compute the measure of a region in four dimensions

I need to be able to calculate an integral with this implicit region: ...
0
votes
1answer
74 views

NIntegrate::femrdim: FiniteElement method can only be applied to regions of embedding dimension 1, 2, or 3

As in the title: I'm trying to Nintegrate over an ImplicitRegion, this error appears. No idea what it means. Nothing in the docs. It appears on this line: ...
4
votes
1answer
64 views

Make MeshRegion/BoundaryMeshRegion work as a graphics primitive in M11

Mathematica 12 has the nice feature that MeshRegion and BoundaryMeshRegion objects render nicely when included as a primitive in ...
5
votes
1answer
94 views

Colors for Regions

I would like to make different components of my 3D regions show in different colors (colours). Here are some dimensions for a bolt, washer and plate. I can make the individual components in different ...
4
votes
1answer
72 views

How to switch off the Mesh on an ellipsoidal RegionPlot3D?

I want to draw 3D ellipsoids, the simplest of which is RegionPlot3D[Ellipsoid[{0, 0, 0}, IdentityMatrix[3]], Mesh -> None] How can I switch off the black mesh?...
1
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2answers
52 views

Problem defining a polygon

I have two polygons that are very similar as: ...
0
votes
0answers
33 views

RegionPlot with FindMaximum

I don't understand why each time I'm launching this computation Mathematica buggs and I get a message from Windows that the Kernel stopped working... I'm trying to get a map of where the value of ...
0
votes
0answers
25 views

RegionPlot fails

Consider a function f[x_,y_]:=NIntegrate[g[x,y,z],{z,1.1*x,3000}] where g[x,y,z] is some function. The function f[x,y] is smooth and works perfectly when Plot it....
1
vote
2answers
53 views

Finding positive region of continous function

I want to find (and plot) the positive region (within a certain domain say x<3,y<3) of a function ...
0
votes
0answers
33 views

How to set integration limits

Consider the functions ...
1
vote
1answer
78 views

How can I remove a certain point from a 2D region?

I started experimenting with Mathematica a few months ago in college (It's my first year in electronics engineering, so I'm not even close to an advanced user's profile yet). My problem comes when I ...
4
votes
1answer
73 views

How to make a 2D region on the surface of 3D volume?

I am trying to define an area on a volume that I can use for a boundary condition. This is a minimum working example to show the problem my real problem involves stress analysis. I define a region ...
1
vote
1answer
70 views

Dashing an area in a region plot where the region is not defined [duplicate]

Can someone tell me how to dash a part of a region where the function doesn´t exist? An example 1 >= x^2 + x > y, where y...
1
vote
1answer
51 views

Differing RegionIntersection of Lines vs HalfLines

I seem to get slightly different result when intersecting line segments vs interesting (infinite) lines. ...
2
votes
2answers
106 views

Fill points into a pre-rotated convex Dodecahedron

I am trying to fill a rotated convex polyhedron with points. This functions well in the unrotated case: ...
3
votes
2answers
128 views

Visualizing a complicated Region

I was given the problem to find the area bounded by the polar curve $$r=\frac{1}{2}+\frac{3}{2}\cos(\theta)$$ which looks like            &...
1
vote
0answers
29 views

RegionDifference not working with one Cuboid and large number of embedded cylinders

I am trying to create a Cuboid with embedded hollow cylindrical regions. It seems to work fine when I use a relatively small number of cylinders (about 20) but does not work when I use a large number ...