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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.

3
votes
1answer
64 views

How to find the cells of a region that intersect a line?

I'm looking for the fastest way to access the mesh cell (i.e. polygon) in a Region that intersects a Line in 3D. For example, <...
1
vote
1answer
85 views

Computing area below 2D function

I'm trying to find an area (in η and y plane) in which the below function is >=0 ...
1
vote
0answers
21 views

Issue with RegionFunction in DensityPlot

I don't get why RegionFunction troncates even the places where x+y<1 ! ...
3
votes
2answers
77 views

Plot the region covered by a map?

Suppose we consider two dimensional cartesian coordinates x,y and pick a parametrization x = r Cos[phi]; y = r Sin[phi]; I ...
1
vote
1answer
41 views

DiscretizeRegion was unable to discretize the region ImplicitRegion

I'm trying to model a 3D die with ImplicitRegion[] in order to find out its center of mass. However, when I apply ...
2
votes
2answers
55 views

Vertices of a Rotated Polyhedron

I am attempting to geometrically transform a polyhedron (namely rotate and translate the polyhedron in global coordinates) and than find the new vertices. Here is what I have so far, but I am stuck at ...
0
votes
1answer
21 views

DelaunayMesh error : EmptyRegion

What is wrong with the following list of points? When I apply DelaunayMesh[listPoints] I get the error ...
6
votes
3answers
89 views

Sometimes Region can't build right region

During my work with NDSolveFEM I found strange behavior of function Region. ...
3
votes
1answer
45 views

Plot shown by Region does not show the full region

Why does the plot produced by the following code not contain the point {0. 0}? ...
3
votes
1answer
54 views

RegionCentroid issue

This example shows an unexpected result from RegionCentroid: ...
3
votes
1answer
46 views

RegionFunction doesn't work in ListContourPlot if also using ScalingFunctions

I am making a contour plot out of a list of values of the form {{x1,y1,f1},{x2,y2,f2},…} I want to plot this on a log log scale so I specify ...
0
votes
1answer
42 views

Plotting the intersection of a ball and a plane

I want to draw a semi-transparent ball and highlight its intersection with a plane. ...
0
votes
0answers
43 views

Animating a Sphere and Creating Static Plot Lines

I have a data set $\xi(t)$ for some numbers that I generated, and let's just say they're wholly positive numbers for now such that we can make $\xi$ like the following: ...
1
vote
1answer
99 views

Not getting the correct domain for an ODE [closed]

I want to find the domain of the the ODE $y\,= (y \operatorname{Ln} (y))/x$ and visualize it. A = FunctionDomain[(y Log[y])/x, {x, y}] ...
0
votes
2answers
31 views

Shading between two regions of two separate parametric curves/function

I have two long functions g12 and g14 in terms of g2: ...
0
votes
0answers
37 views

Understanding BoundaryMeshRegion error

I am trying to calculate the difference between two Cuboids: ...
1
vote
2answers
64 views

Plotting dynamic variable generated by checking Region intersections

I have been trying to plot a variable which is nested inside a manipulate. Here is a simplified version of the program. ...
1
vote
1answer
37 views

Plotting RegionPlot3D within a certain radius

I have a RegionPlot3D: ...
0
votes
1answer
77 views

Why is RegionIntersection failing on my custom Region?

I load a custom region, specified as BoundaryMeshRegion R = Import["C:\\data\\Profile.stl", "BoundaryMeshRegion"] and I try ...
0
votes
0answers
15 views

Using RegionPlot with NIntegrate causes symbolic evaluation when integrating

I am trying to plot the regions when a certain integral is positive. Because the function has many parameters I am passing the values through two sets of rules, one containing the pair of values I ...
6
votes
1answer
105 views

ElementMesh from ImplicitRegion cuts corners of region

I'm trying to define a region within a cell and below a level set of a function using ImplicitRegion and ToElementMesh. Here I ...
0
votes
2answers
41 views

How to compare ImplicitRegion with empty region?

I have the following function using ImplicitRegion: ...
1
vote
1answer
58 views

ImplicitRegion evaluates the region incorrectly when it must be empty

Consider the following implicit region: ...
1
vote
0answers
35 views

Different values of the numeric integral evaluated by using different methods

Consider the space of three variables $x,y,z$ defined in the ranges $$ \tag 1 x \in (0,\pi), \quad y \in (0,\pi), \quad z\in (0,2\pi), $$ and the following UnitStep ...
2
votes
1answer
33 views

Regions conjunction - for what reason are there so many vertices? [closed]

I try to plot the intersection of some regions but RegionPlot does something weird: conjunction doesn't actually match the area: ...
0
votes
1answer
38 views

Problem with region plot

I have a function f[x,y] involving numerical integration. It returns values for any values of x and y well, and if I want to plot its as a function of one of ...
2
votes
1answer
51 views

Find region of given value for linear Interpolation function

Summary: How do I find the (possibly disconnected) region(s) where a linear interpolating function is between two specified values? Example: ...
4
votes
1answer
42 views

Simplify behavior: assumption as Interval versus assumption as bounds

I am using MMA V11.2 under Linux I am surprised by this: ...
1
vote
1answer
57 views

Triangulations/quadrangulations of polygon

Is there a nice way I can find all possible triangulations (or quadrangulations) of a polygon (say 10-gon)? I want to have all possible diagrams with the diagonals marked (i.e. with unique name). ...
1
vote
0answers
27 views

Unexpected behaviour of RegionFunction in 3D Plots [duplicate]

This is a continuation of a similar problem I had posted earlier. I am trying to plot a function defined in a specific parameter space using the RegionFunction ...
2
votes
0answers
49 views

Unexpected behaviour of RegionFunction in 3D plot

I am trying to plot a function defined in a specific parameter space using the RegionFunction option in Plot3D. So, this is how ...
8
votes
2answers
132 views

Detect and fix invalid polygon

I have a polygon given by ...
10
votes
2answers
289 views

Bound surface limits to a function

Consider the following plot of two surfaces ...
7
votes
2answers
164 views

ToElementMesh ignores Boundaries and MeshRefinemet

I'm building a mesh of a pit storage in Mathematica which I then export to another FEM-software. I follow the workflow for creating a ElementMesh from the documentation, but it won't work in the way ...
7
votes
2answers
121 views

MomentOfInertia for Polyhedra incorrectly computed?

The moment of inertia for Regions seems to be wrongly calculated. Simple example: ...
2
votes
1answer
99 views

Why this “is not a correctly specified region”?

I want to subtract one Cuboid[] form another Cuboid[]. This is the code I use: ...
2
votes
2answers
59 views

Using a table within a RegionPlot3D to plot multiple cubes

Here's some code that will produce a cube: ...
1
vote
0answers
50 views

Regions, Mesh Regions, and Graphics

This behavior seems inconsistent to me: ...
1
vote
2answers
64 views

Basic 3D Graphics Question

This is probably a very basic question, but I haven't been able to get it to work yet. I am trying to create a filled 3D space in the region $\qquad 0.1 < x < 9.2,\ 0.026 < y < 28.97,\ 0 &...
10
votes
3answers
199 views

RegionMember[ ] in polygon

I am seeing a difference in RegionMember[ ] testing a point inside a 3-vertex polygon and testing a point inside a more complex polygon: ...
3
votes
1answer
73 views

BooleanRegion with .stl files does not work

Im trying to use BooleanRegion[] on an .stl file. The imported .stl file is called pores and is of type MeshRegion (...
1
vote
1answer
74 views

Create a 2D region plot with 3 variables, 2 sharing the same axis

I have a region with 3 variables: x, s3 and s4. The value of s3 depends on x and the value of s4 depends on both s3 and x. The full region is as follows: ...
2
votes
2answers
72 views

Illustrate homework (integral region with implicit region)

I must integrate: $$ \int \int_D x^2y^2 dx dy$$ in the first quadrant. This is a triangle with vertices in $(0,0)$, $(0,1)$ and $(1,0)$. I tried to draw it in mathematica with implicit region: <...
1
vote
2answers
98 views

Integration in a region?

f[x_, y_] := NMinimize[{Sin[a x y], 1 < a < 5}, {a}][[1]] NIntegrate[If[f[x, y] > 0, 1, 0], {x, 0, 1}, {y, 0, 1}] I want to perform integration in the ...
2
votes
1answer
61 views

RegionIntersection of Regions

This code does what I expected: It displays the region of intersection between two disks: ...
3
votes
4answers
161 views

How to print all the integer points on and inside the graph of the equation?

Consider an equation $(x-1)^2/25+(y+2)^2/9=1$. (x-1)^2/25+(y+2)^2/9==1 How can one print all the integer points on and inside the graph of the equation? I ...
8
votes
3answers
175 views

Trouble meshing a Corbino disc

I am trying to simulate current flow using FEM through this particular device (a Corbino disk) and I have difficulties generating the mesh for it. Here is the region: ...
1
vote
0answers
104 views

Ternary diagram

I'd like to make a RegionPlot on a ternary diagram, meaning in a triangle where the axis are $x,y,z$, which are related by $x+y+z=1$. The RegionPlot would have as a condition $x^2+y^2<1$ for ...
3
votes
0answers
63 views

Finding the shortest distance of two points and an area

So I have a region defined by something like MeshRegion[{{0, 0}, {1, 1}, {2, 1/2}, {2, -1/2}}, {Line[{1, 2}], Line[{2, 3}], Line[{3, 4}], Line[{4, 1}]}], and two ...
5
votes
2answers
255 views

Is it possible to have a region plot with logarithmic scales?

How can I have a region plot with the logarithmic axis? In the following, I have brought the original case which I want to be logarithmic. In this case, I have a density plot and a region plot that ...