# All Questions

272 views

### How to reject or repulse some points in a 3D cloud of particles?

I'm having an issue with a 3D distribution of points. The distribution is really nicely looking in Mathematica, but it is used in an OpenGL astronomy program (Celestia) to generate a nebula, with ...
128 views

I'm having some trouble with identical code giving different answers. On a fresh kernel (MM 9.0.0.0, Windows 64-bit), running the same code, copy-paste, gives two different answers: ...
456 views

### Running a Numerical Simulation on a System of Differential Equations with unique initial conditions

I have a system of differential equations as follows: ...
194 views

### Remove the white margins of a Graphics3D figure

If the option Boxed is set to be False in Graphics3D, additional white margins may appear as ...
178 views

### Why won't ContourPlot accept a variable argument? [duplicate]

I have a list of linear inequalities which describe a (polygonal) region. I can use RegionPlot to visualize this region; but I'd also like to overlay this plot with ...
234 views

### Keep Ordering of Bra Ket When Printing

I would like to keep the ordering of the bra ket-print but right now this doesn't happen. Any Idea? I tried playing with HoldForm but then i could evaluate the expression inside properly ...
157 views

### EmpiricalDistribution for Gini Coefficient Runs Slow

I am repurposing code that I found in this blog post (http://datavoreconsulting.com/sports/gini-coefficients-and-the-olympic-medal-race/) to generate the Gini coefficient for other data sets I am ...
284 views

### Integration gives ComplexInfinity when it shouldn't

A simple example of my problem is that Assuming[k ∈ Reals, Integrate[Exp[l]/((1 + Exp[l])*Exp[k*l]), l]] /. {k -> 2} gives ...
278 views

### Find all permutations with a condition

How can I find all the permutations of {a, b, c} where a + b + c = n? For instance: if ...
849 views

### How to simplify a complicated Sum in terms of power Sums?

For example, I have: $a=\sum _{r=1}^n x_r \left(\left(\sum _{i=1}^n x_i-x_r\right){}^2-\sum _{i=1}^n x_i^2\right)$ ...
297 views

### Cumulative frequency plot

I have the following data: data = {{0, 0}, {20, 1.4}, {25, 9.8}, {30, 32.2}, {35, 38.2}, {40, 15.6}, {45, 2.7}, {50, 0.1}}; where the second coordinates are ...
171 views

### How to show error messages in current notebook?

I would like Mathematica to print error messages in current notebook together with output. This is default option in Mathematica, but recently I turned it off somehow. Now, I am getting output in ...
57 views

### Avoiding re-evaluation of RegionPlot3D on a second computer

After running a RegionPlot3D named "testplot" on my desktop, I followed an earlier suggestion from the forum and saved it using: ...
220 views

### Interpolation on large 2D list results in erratic function

Previously, I've had problems with Mathematica interpolating and plotting 3D lists, but I finally managed to do so by rescaling the x and y-axes with the help of the methods proposed here. Now my ...
366 views

### Using Manipulate to vary the frequency of a sound produced by SoundNote[]

I have tried various ways to combine Manipulate and Sound/SoundNote that would allow me to vary the frequency of a sound while it is being produced. The addition of Dynamic didn't help, but did ...
133 views

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169 views

### Plot3D list elements

I've been having some trouble with Plot3D. I have a quite complex function of two variables (actually three but the first one doesn't matter) that returns a list ...
105 views

### Exporting data from different notebooks to a common file

I am doing some calculations from different notebooks. I need to export the results from all those notebooks in columns of the same file, like a1 b1 c1 a2 b2 c2 a3 b3 c3 . . . where a, b ...
293 views

### Select rows from table by keys

I am looking for a way to iteratively select all sublists with the same ID (my 1st column, residual columns are AbsoluteTime entries). First, I obtained the list of ...
460 views

### Transparent Cylinder with Dashed Edges only

I would like to have that kind of cylinder with Dashed edges (including the bellow inner ring): I've been trying that: ...
164 views

### Interpolating a Bivariate Polynomial over a Finite Field

Let $F=GF(p)$ be a finite field, $p$ prime and write $F^\times=\{x_1,\ldots,x_n\}$. I'm trying to implement an earlier version of Sudan's list-decoding algorithm for Reed Solomon Codes ...
268 views

### Reduce the output from tuples by including symmetry?

I need all the possible 3x3 binary tensors, but I'd like to have this account for symmetries. I've started by using the Tuples command. Tuples[{1, 0}, {3, 3}] ...
102 views

### Cell background color changes cell layout

When I change the background color of a cell like in the colored cells become slightly indented and their line spacing is increased. How can I change the cell background color while keeping the ...
513 views

### OpenSCAD like functionality with Mathematica?

I keep seeing reference to use of Mathematica as a CAD tool (for instance: http://www.makerbot.com/support/guides/design/). I'd like to use it as such if feasible, but I'm having trouble locating ...
377 views

### Horrific Looking Contour Integral in Mathematica Plot:

I'm attempting to display the geometric meaning of a contour integral but as you can see, the typesetting of the contour integral (created via the Epilog function) looks awful because the contour ...
193 views

### How to format problem in WolframAlpha? [closed]

Is there a way to enter this problem in WolframAlpha?: the sum of the reciprocals of two consecutive integers is -9/20. Find the two integers.
667 views

### Why doesn't my script work when I redirect stdout?

I'm using Mathematica Home Edition 9.0.1 on Mac OS X 10.8.2. I have this script: ...
237 views

### Launching remote slave kernels on HPC causes slow down

I had a post earlier regarding how I can run Mathematica at a HPC cluster (running PBSpro) by having a single MathKernel launch ...
663 views

### Dashed mesh behind 3D object

I am trying to create a simple, almost transparent 3D sphere with a mesh that is made of solid lines if they are on the front surface (i.e. if they are directly visible) and of dashed lines if those ...
131 views

### Avoiding the re-evaluation of a RegionPlot3D

Is there a simple way to save the output from RegionPlot3D so as to avoid re-evaluating when the notebook is re-opened and Show ...
48 views

### Definition of differential operators [duplicate]

I am curious how differential operators are defined in Mathematica. More specifically, if the Laplacian function wasn't available, how would one go on to define such a function in Mathematica directly ...
172 views

### Convert logical relational expression to / from disjunctive and conjunctive forms?

I would like to convert logical relational expressions in disjunctive form, e.g., $$(x \lt -1) \lor (-1 \lt x \lt +1) \lor (x \gt +1)$$ into conjunctive form, e.g., $$(x \ne -1) \land (x \ne +1)$$ ...
199 views

### Finding rational roots to an equation (univariate) [closed]

So I'm using Mathematica 7 for Students and I'm using the Root function to find the roots of an equation over the rational numbers: $$225x^6 -343 = 0$$ I created ...
154 views

### Solving a system consisting of an ODE and a non-differential equation

I would like to solve the following system of equations: y'[t] == x[t]*y[t] - x[t]; 10 == x[t]*y[t]/(x[t] + y[t]) + x[t]/(x[t] + y[t]^2) Is there any way to ...
327 views

### RefProp in Mathematica

RefProp by NIST is a program that calculates the thermodynamic properties of fluids. I need to call certain RefProp functions ...
549 views

### Graphical Plots of PDF and CDF

I have a joint density and distribution function that I want to plot in a meaningful way, (i.e., want to be able to see how the functions behaves as changes in x and y happen simultaneously. If ...
1k views

### Spiral pattern and Fibonacci numbers

I'm want to generate a 2D spiral pattern like the the one shown in the following figure. I can generate the spirals one by one, but I think there ought to be a more efficient method for generating ...
344 views

### Efficiently appending points to a NearestFunction

I have a program which works with a list of points (in 3D, but it could be in 1D as well, it won't make a difference). Within a loop, it keeps adding new points to the list. To calculate the ...
3k views

### Solving a tridiagonal system of linear equations using the Thomas algorithm

I'm trying to write a function that can solve a tridiagonal system of linear equations using the Thomas algorithm. It basically solves the following equation. (Details can be found at the Wiki page ...
137 views

### Version 8.0 integrates but Version 9.0.1 doesn't

I am trying to run the following integral in version 9.0, but it fails: ...
201 views

### Manipulating a Graphics3D output with a large number of geometric primitives

I'm attempting to view and rotate a Graphics3D object with a very large set of geometric primitives ($\approx 10^6$ objects such as spheres or lines), and everything is functioning very slowly. Are ...
714 views

### How to draw a higher-genus surface

NB: By higher-genus surface, I mean a closed orientable surface of genus at least 2. This question has come up before on math.SE, and even MathOverflow, but most posters suggested using either ...
99 views

### How can PixelConstrained be emulated with DensityHistogram?

This DensityHistogram doesn't display very well. Some bins are shown much larger than others and, oddly, empty bins appear to be drawn smaller than occupied bins. ...
866 views

### Exporting a .xlsx file with about 500 columns

When I want to Export["text.xlsx", data] where data is a matrix with 500 columns and 10000 rows, I get the error message: ...
70 views

### How to define the tangent gradient operator? [duplicate]

I would like to define a new differential operator that is the tangent gradient for a curve $\Sigma$. This is defined as $$\nabla_\Sigma=\mathbf{P}\nabla$$ where $\mathbf{P}$ is the projection ...
77 views

### SetDelayed and avoiding function calls through memoization [duplicate]

I am fairly new to Mathematica. I am working my way through a number of books. I have been looking at the use of SetDelayed and want to confirm that my ...
152 views

### Problem when merging cells including commentary

This is a more of a problem report than a question. When merging the two cells Cell1: foo (*foobar*) bar and Cell2: ...
470 views

### How to change default settings of cell formatting?

I find font size of Text cells too small and I like displaying them with background colour... I've read this question and learned about ...
### Solving $k\log(n) - k\log(k) \leq u$
How can I persuade Mathematica to help me find solutions to the inequality $k\ln(n) - k\ln(k) \leq u$ over the reals, assuming $u \geq n \geq k \geq 1$. When I evaluate ...