3
votes
2answers
995 views

Eliminate doesn't work in Mathematica

Hello Mathematica users, I have problems trying to eliminate variable $Q(x,y)$ froma PDE, but Mathematica output is just True. The problem is that I already found ...
2
votes
2answers
372 views

Using Periodogram to investigate the seasonality of the data

After asking how to get rid of the seasonality of this set of data, I'd like to ask how to investigate the seasonality in data using Mathematica. Which tool would you use to study seasonality? I.e. ...
2
votes
2answers
914 views

Dynamically choosing which Manipulate controls to use

I have some stuff I would like to manipulate, using two different kinds of control, one at a time, using another variable as a switch. These controls are similar in principle to ...
2
votes
2answers
122 views

How to copy Coordinates of “Get Coordinates” in Figure?

I am trying to reproduce the answer here about Recovering data points from an image. I click the figure and press "Get Coordinates". I would like to copy the four coordinates by CTRL-C and then paste ...
2
votes
2answers
378 views

Fastest way to concatenate many text files in a given directory

I have about 1 million .txt text files in a directory which I would like to all concatenate in one single text file (separated by a newline character "\n"). Because of the number of files and their ...
2
votes
1answer
5k views

Forcing FindRoot to return only real solutions

FindRoot documentation reports that if the equation and the initial point are reals, the solutions are searched in the real domain. However, in the following case I ...
1
vote
1answer
733 views

Derivative of an expression containing a symbolic sum [duplicate]

Is there a general pattern for working with symbolic sums in Mathematica? For example here's a derivative I want to compute: ...
1
vote
4answers
3k views

How do I plot x[t] vs. x'[t] (where x[t] and x'[t] are solutions to NDSolve)?

I have a differential equation which I solved using NDSolve. I can easily plot x[t] vs. t, x'[t] vs. t, but.... how do I plot x[t] vs. x'[t]? I tried using the Evaluate function to simplify things, ...
1
vote
1answer
310 views

Performance of compiled functions (Project Euler No14)

I was playing around with the project euler problem 14. The solution I came up with is listed below as cf1. The solution works fine but I get the compiler warning: ...
1
vote
1answer
270 views

Basins of attraction of equilibrium points

The Henon-Heiles potential is the following V = 1/2*(x^2 + y^2) - y*(1/3*y^2 - x^2); which has four equilibrium points ...
1
vote
0answers
74 views

Set form of all output to InputForm

I try to interact with mathematica using MathLink for symbolic computations. By default it returns strings such as 2\012-1 + E\012-------\012 3\012 E if the ...
32
votes
1answer
772 views

Version 10 cannot print properly?

Bug introduced in 10.0 and persisting through 10.4 or later I have two problems with printing in version 10. First, I can't print correctly with a setting of printing scale For example, I have ...
30
votes
2answers
607 views

GroupBy twice gives different results

Bug introduced in 7.0 or earlier and persisting through 10.4 or later It took me quite a lot of time to finally trace down to this strange output. I really don't know why. First, I create a list ...
19
votes
1answer
600 views

When exporting an (animated) GIF, is it possible to specify the size of the color palette?

I've exported an animation to animated GIF, which generated a 15mb file. I've been asked if I could regenerate the file, limiting it to only 16 colors, but I can't find any documentation on how I ...
18
votes
3answers
1k views

Highlighting individual countries on a world map

Consider the following list of countries which I would like to highlight on a world map: ...
18
votes
2answers
218 views

How to avoid the wiggly text on Ticks and Labels when rotating 3D objects

Motivation I'm trying to do a nice animation of the rotation of a ParametricPlot3D . My problem is that the Ticks numbers and <...
18
votes
4answers
1k views

How can I randomly generate a unique, unused symbol?

In a previous question on collecting terms for a multivariable polynomial, I answered with a solution that required a unused symbol to be used for a temporary substitution and back substitution. It ...
17
votes
3answers
2k views

Effective matrix power like algorithm

First example Suppose you want to calculate the 6th power of some matrix $A$. The brute force attempt of doing this is considering $$(((AA)A)A)A)A$$ which requires a total of 5 matrix multiplications....
17
votes
5answers
651 views

Add a vector to a list of vectors

What is the syntax to add v1 to each vector in v2? I know it has to be simple, but I really have searched and not found it. <...
17
votes
2answers
423 views

Count number of sublists with a total not greater than a given max

Suppose I have a list of positive integers: data={1, 1, 2, 3, 3, 3, 5, 5, 5, 7, 7, 8, 8, 9, 10, 10, 12, 16, 23} I want to count the number of subsets up to ...
17
votes
2answers
410 views

Messages leak out from Block

Bug introduced in 8.0 or earlier and fixed in 10.1 When assigning message to a symbol localized by Block, I would expect that this message is not accessible ...
17
votes
0answers
149 views

How to keep the ctrl+shift+k help menu remain in display while typing? [closed]

In Mathematica 9, one can type ctrl+shift+k to display menu which has all the possible signatures/definitions for the function or command in question. One can ...
17
votes
1answer
238 views

Aggregation queries on lists of associations in 10.3

Bug introduced in 10.3.0 Some aggregation queries applied to a list of associations (or Dataset's with this structure) lock up the front end or crash the kernel ...
16
votes
5answers
2k views

Measure perimeter of black edge in Mathematica

I have a pattern like the one below. How could I measure the total length of the perimeter of the black/white edge? This would give me a measure of spatial frequency. Any tips would be great! Thanks!
16
votes
5answers
830 views

How do I generate the upper triangular indices from a list?

I have some list {1,2,3}. How do I generate nested pairs such that I get {{1,2},{1,3},{2,3}}? That is I'd like a way to ...
16
votes
0answers
224 views

Exp is slower for some number ranges

I get a hit on performance with the Exp function depending on the range of my inputs. for example, with: ...
16
votes
1answer
1k views

Compact Rational Function Fitting

I have some data from a study that I am trying to fit with a rational function of arbitrary form: $y(x) = \frac{\sum_{i=n}^m A_ix^{i/q}}{\sum_{j=o}^p B_jx^{j/r}}$ where $i$, $j$, $k$, $l$, $m$, $n$, ...
15
votes
6answers
830 views

Matrix Rotation

If I have a matrix of any size, say $\begin{pmatrix} 72 & 32 & 64 \\ 18 & 8 & 16 \\ 63 & 28 & 56 \\ \end{pmatrix}$ $\begin{pmatrix} 72 & 32 \\ 18 & 8 \\ 63 &...
15
votes
1answer
334 views

Bug in plotting function using FindMinimum?

Bug introduced in 10.0 and persisting through 10.3 or later While working on an answer to RegionPlot from NDSolve, I came across this strange behavior of ...
15
votes
3answers
3k views

Creating a Sierpinski gasket with the missing triangles filled in

I'm creating some questions for my math classes. The one below refers to the Sierpinski gasket. I found some great demonstrations to create the gasket. So that's good. Solving the problem is ...
14
votes
1answer
301 views

How to programmatically remove menu items

I would like to do the opposite of what is described here. So rather than add a menu item I would like to programmatically remove one (or more). So given a knowledge of the structure of the menu *.tr ...
14
votes
1answer
554 views

ImageAlign doesn't always work correctly

I've been working with ImageAlign in Mathematica 8 and I'm having trouble getting it working reliably. Perhaps there are some subtleties that I'm not yet aware of? ...
14
votes
2answers
1k views

Is Mathematica a Turing-complete language?

Is Mathematica a Turing-complete language? If so, how can that be proved? If not, why?
14
votes
1answer
434 views

When to use built-in Graph/GraphPlot vs. Combinatorica

What are the pros and cons of using built-in Graph/GraphPlot (and related) types vs. types in the Combinatorica package?
14
votes
1answer
3k views

What method does NDSolve use for solving PDEs?

What is NDSolve's mode of operation? I use it to solve partial differential equations and never gave it too much thought. Recently, I came across this question. ...
14
votes
1answer
154 views

Question about TransitiveReductionGraph

Bug introduced in 10.0 and persisting through 10.4 Note: TransitiveReductionGraph is new in 10.0. In Mathematica 10.0 and 10.1, according to the documentation ...
14
votes
3answers
309 views

How do I put my packages into Dropbox

I don't want to necessarily put my packages in Mathematica's $UserBaseDirectory, which is on my local hard drive. Can I somehow tell Mathematica to look for ...
14
votes
1answer
234 views

Grid cuts my images

Bug introduced in V9.0 or earlier and persisting through V10.4.0 pic2 = ImageResize[ ImageCrop@Rasterize@Graphics@Disk[], {Automatic, 40}] ...
14
votes
2answers
643 views

Solve differential equation using a integral form boundary condition

I have a second order differential equation and I want to solve it analytically (DSolve) and numerically (NDSolve) with ...
14
votes
1answer
462 views

How to enlarge Mathematica's knowledge about certain functions?

I'm often troubled with the following task. I need to carry out symbolical computations involving certain special functions. Let me take as an example Barnes gamma-function. It is included in ...
14
votes
1answer
728 views

How to run an external program in parallel with a Mathematica package?

Under Mathematica 8 (Linux x84_64) I was able to run an external program in parallel from a Mathematica package. However this procedure breaks down under Mathematica 9. Within my Mathematica package ...
13
votes
1answer
240 views

Layout a second graph of the same nodes in the same way

I have a number of graphs with the same nodes. I would like to be able to somehow save the layout that results from the spring embedded results of one graph (the first image), and have the other ...
13
votes
0answers
179 views

func::usage needs to be run twice? [duplicate]

There is an annoying problem that I can't figure out why it's happening. I have defined a usage for a my function tensorA: ...
13
votes
5answers
258 views

Prevent Plus from threading

This is probably a very simple question, but I couldn't find a duplicate. As everybody knows, {x, y} + v gives {x + v, y + v}. ...
13
votes
1answer
242 views

Nearest Kronecker Product

Some people (see The ubiquitous Kronecker product by Van Loan) have worked on finding two matrices $\mathbf A$,$\mathbf B$ of specified size whose tensor product $\mathbf A\otimes\mathbf B$ is closest ...
13
votes
5answers
862 views

Animate point going around a triangle

How can I animate a point moving on a triangle's sides? I can generate a triangle and point, but I have no idea how to define point movement. I'm guessing that I have to use $\sin$ and $\cos$ in ...
13
votes
2answers
2k views

Creating 3D dice

How to create an image of a 3D die from the 2D images? There is an example in the Documentation Center I tried but it doesn't work.
13
votes
6answers
757 views

Elegantly split a matrix into positive and negative parts?

I have a matrix $M$ of real components, and I want to split it into two matrices $M^+$ and $M^-$ of the same dimensions as $M$, where $M^+$ contains the positive components of $M$ (the remaining ...
13
votes
9answers
516 views

Dropping n consecutive terms from a list periodically

Suppose I have the following list lis = Range[100]; and I want to remove n consecutive terms periodically from the list. For example suppose I want to drop terms ...
13
votes
4answers
416 views

Unencoding encoded URLs in a function

Is there a built-in function for decoding encoded URLs in Mathematica? I would like to convert an encoded URL, for example ...

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