# Tagged Questions

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### “Tag list in … is protected error” Small question [duplicate]

I am trying to do something very simple. I just would like to construct a translation matrix where I can chose my translation parameters: ...
75 views

### Help changing coordinates back after partitioning an image?

I'm new to Mathematica. I was just wondering how I could change the coordinates back after I partitioned an image. For example, if I used ImagePartition[] to split ...
37 views

### VectorPlot3D in cylindrical coordinates

I am using VectorPlot3D to plot fluid flows (in the form of a velocity field), however, I go through quite an involved process to convert flows in Cylindrical ...
37 views

### Coordinate transformation for gradients expressions [duplicate]

Let's suppose I have an expression in cartesian coordinates, involving gradients, such as: F[x,y]:=D[f[x,y],x]/D[f[x,y],y]+D[f[x,y],y,y] f[x,y] Now, I would like ...
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### Inverse substitution polar-cartesian

When I have an expression in polar coordinates and I substitute the definition of $r$ and $\phi$, I get the corresponding expression in polar coordinates. I would like to go back and obtain the same ...
128 views

### How to extract coordinates {x,y,z} from Raster3D

I want to extract coordinates out of a Raster3D. It is possible to extract coordinates out of an Image3D by using ...
419 views

### Integrate to calculate enclosed area

I am trying to 'use an integral in polar coordinates to calculate the area enclosed by this curve': The curve is: $r=\sin 2\theta$, $\theta \in [0, \pi]$ which I believe is already in polar form. I ...
144 views

### How to guarantee the point's position is fixed in the Graphics and Image

SeedRandom[8] plot = ParametricPlot[ Evaluate@BezierFunction[temPoint = RandomReal[{-50, 50}, {5, 2}]][ t], {t, 0, 1}, AxesOrigin -> {0, 0}] We can ...
190 views

### Why PolarPlot can have negative $r$?

Suppose a simple equation in Cartesian coordinate: $$(x^2+ y^2)^{3/2} = x y$$ In polar coordinate the equation becomes $r = \cos(\theta) \sin(\theta)$. When I plot both, the one in polar coordinate ...
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### A little confused about coordinate conversion

I'm not entirely sure how to convert from spherical coordinates to Cartesian coordinates, I believe the way to do it is by using the following code: ...
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### Why is the range from $-\pi$ to $\pi$ in polar coordinates?

When I run this code FromPolarCoordinates /@ {{3/2, \[Pi]/3}, {3/2, (5 \[Pi])/3}} Then I search the documentation of ...
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### Changing from Cartesian to polar coordinates in partial differential equation [duplicate]

I have a partial differential equation: $$\left(x^2+y^2\right)\frac{{{\partial ^2}u(x,y)}}{{\partial {x^2}}} + x^2\frac{{{\partial ^2}u(x,y)}}{{\partial {y^2}}}=0$$ How to change from Cartesian to ...
105 views

### Angle between two vectors in spherical coordinates [closed]

I have two vectors: H = {1, 0, π/4}; EA = {1, 0, 0}; Which I want to be in {r, Phi, Theta} - which would should give an angle between the two vectors as ...
143 views

### Draw Vectors in Spherical Shell and then Animate

I want to draw three vectors inside a spherical shell. One of the vectors will be moving, the others will be stationary. However, the animation is the next step. For now, I would like to get the ...
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### ImageForwardTransformation produces strange artifacts

I am trying to manipulate an image in equirectangular projection with ImageForwardTransformation. I want to change the projection's inclination to the ecliptic. For ...
365 views

### Map points on a square onto a Torus

I would like to create a 3D torus plot from a 2D graphic. This 2D original plot is a bit complex, and I haven't a clue how could transform it to a torus. The below code, from this article posted on ...
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I have: ...
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### Non-rectilinear integration of InterpolatingFunction

Bug introduced in 7 or earlier and persisting through 10.3.1 [CASE:3487737] I have a 2-d array that I would like to resample into a different coordinate system and integrate along one of the new ...
317 views

### Coordinate system transformation problem (about Euler angle)

This question comes from the work that constructing the general cylinder by the NURBS. I have implemented the point-set $P_1,P_2,\cdots,P_n$ that in the $O-xyz$ plane, now I want to implement the ...
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### Cylindrical Coordinates with NDSolveValue [closed]

Can anyone help me figure out how to set up a solution for NDSolveValue that incorporates the use of Cylindrical Coordinates. I tried using SetCoordinates[Cylindrical] but it is not working (as in it ...
154 views

### ListDensityPlot in Polar coordinates with a higher efficiency

I have data like this f[r,theta] and cells number are about 600*600 (uniform mesh) The original data has the property of uniform mesh for ...
382 views

### Using Grad, Div, etc in polar coordinates

I'm trying to use the newish functions Grad and Div to work with a PDE with circular or spherical symmetry and getting what looks to me like a wrong result. However, I'm not sure of this--perhaps I ...
111 views

### Integration of angular distribution along cartesian axis

I am plotting an anisotropy distribution function as color coding on the surface of a unit sphere with this code: ...
101 views

### Why does a transform from polar coordinates using TransformedField not agree with by-hand calculation?

I have the following (simple) system of ODE's that I wish to express in Cartesian coordinates: \begin{align*} r' &= r(1-r)\\ \theta' &= 1 \end{align*} Working it out by hand, by ...
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### Analogue for Maple's dchange - change of variables in differential expressions

Maple owns an interesting function called dchange which can change the variables of differential equations, but there seems to be no such function in Mathematica. ...
228 views

### Translating Histogram

SeedRandom[1]; RandomVariate[NormalDistribution[], 100]; Histogram[%, Automatic, "Probability"] The above code produces a histogram like I want to translate ...
257 views

### Plot a parametric equation in cylindrical coordinates

I'm looking for a way to plot this parametric equation on cylindrical coordinates. r = e^t theta = t+1 z = e^2t Any help would be appreciated
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### Change of variables—Galilean transformation

I have a function of two variables, f[x, y], and I wish to do a Galilean transformation, i.e., y = z - v t, where ...
281 views

### Is there an easy way to transform unit vectors from spherical to Cartesian coordinates? [duplicate]

Is there a built-in function on Mathematica that will transform unit vectors from one coordinate system to another? I have a vector expressed in spherical coordinates, and I would like to find the ...
492 views

### How can I define or use a new coordinate system in Mathematica?

I want to use the dipole coordinate system as defined in this paper: http://arxiv.org/abs/physics/0606044 I see that Mathematica can do all kinds of vector analysis using different kinds of ...
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### Von Neumann's method to generate points uniformly distributed on a region of a n-sphere surface

I am trying to generate points uniformly distributed on a region of a single n-sphere surface (all angles in hyperspheric coordinates are between 0 and Pi/2). I decided to use von Neumann's method ...
287 views

### How can I output the coordinates of a city in coordinates of the Mercator projection?

On Mathematica version 8, I would like to use CountryData and CityData to mark Paris on a polygon map of France in the Mercator ...
122 views

### How to apply a transformation to a grid?

I would like to apply a coordinate transformation, visualised as an action on a two-dimensional grid like The particular example above is x^\mu \mapsto \frac{x^\mu - b^\mu x^2}{1-b\cdot x+ b^2 ...
332 views

### Astronomy: Transform coordinates from horizon to equatorial

I'm using Mathematica 10. Giving a longitude & latitude on Earth, giving a local time, how can I transform Horizon Coordinte (az , alt) to Equatorial Coordinate (RA , DEC). Use function so I can ...
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### coordinate system problem [duplicate]

I had an issue about the coordinate system of mathematica. I have a {800,600} image acquired with a camera. The projection matrix P of the camera is calculated using the calibration task. Now, when I ...
206 views

### Different between two graph in the Polar Plane

How can I plot $\theta=\cos r$ in polar plane? Of course I know that is different with $r=\cos \theta.$
283 views

### Plotting in Elliptical coordinate system

I want to plot an equation in elliptical coordinates. In the traditional elliptical system, Ellipse and hyperbola shares the same confocal point. Is there a plot function that draws a function in this ...
204 views

### CoordinateTransformData (cartesian to spherical)

I am using Mathematica v9.0.1.0 and wanted to compare Mathematica's CoordinateTransformData command to Matlab's cart2sph. (Note ...
402 views

### Compose many Geometric Transformations for 3D Graphics

I'm struggling to understand what would be a good way to compose several geometrical transformations to create a single TransformationFunction to be applied to a <...
320 views

### Order contour points in clockwise

I want to describe shape of an object using contour points descriptor. Given a silhouette (image black white of an object), I extrait the contour points using EdgeDetect[] fonction. After that, I need ...
644 views

### Find a right angled triangle

If I am given 10 points in the coordinate system in the for (x,y); where x is the x-coordinate and ...
196 views

### Convert Locator (x,y) values to Lat/Lon as per GetCoordinates on Map

I want to convert the (x,y) coordinates you get from using a locator on a map to Lat/Lon coordinates - exactly like the GetCoordinates tool does when you right click on a map. ...
373 views

### Derivatives with respect to Cartesian coordinates of functions in spherical coordinates

This seems to me to be a common task, and the more surprised I was to not have found much on this. Suppose I have an expression f in spherical coordinates ...
825 views

### ImageTransformation: polar to cartesian

I am working on something that requires the polar transformation of some images. I implemented this transformation with ImageTransformation: ...
746 views

### Mapping data on Archimedes' spiral

I would like to map my data on Archimedes' spiral and preserve the distance between points on the curve. The test data consists of 20 evenly spaced {x,y} ...
335 views

### Using spherical derivatives with NDSolve

I am trying to plot the path of an object around a centre of mass. Obviously this needs spherical coordinates. The problem I encounter is with the derivatives. The Derivatives in spherical coordinates ...
246 views

### Plotting in projective space

I am having difficulty figuring out how to plot to projective space. Suppose I have a region which I have plotted such as: ...
106 views

### Geometric Transformation not working - degenerate points?

I've successfully used FindGeometricTransformation to project the simplex triangle onto the x-y plane: ...