8
votes
1answer
447 views

Issue with the NDSolve code

With this procedure, one may determine an eigen-value function $R(a)$ for any given $\Xi$ (say 0, 25, 50, 75, 100) ...
1
vote
1answer
217 views

Create Slider to start/stop/move Point

I want to be able to start, stop, and move the dynamically moving point simultaneously in both animations. The "PlayPauseButton" in the animations only controls the given animation. Indeed, I want ...
4
votes
2answers
150 views

Non-convergance of the solution of the 1+1 partial differential equation

I am stacked with a partial differential equation as follows: This is the $\LaTeX$ expression for the equation $$ \frac{\partial y}{\partial t}=\frac{\partial^2 y(x,t)}{\partial x^2} -\left(a-\frac{1}...
4
votes
1answer
207 views

List all possible elements of a set

I have this two sets: $A = \{\emptyset, \{\emptyset\}, \{\{\emptyset\}, \emptyset\}\}$ $B = \{\{x, \{x, y\}\} | x \in A, y \in A\}$ Now I want to list all possible elements that are in $B$. How do ...
2
votes
2answers
217 views

Limit of integral gives incorrect output

I'm trying to evaluate $\lim_{e\to 0} \, \frac{i}{e}\int_{\pi }^0 \frac{1-\exp (i e \exp (i \theta ))}{\exp (i \theta )} \, d\theta$ with Mathematica 9.0.1.0 on OS X. However, I get "Undefined" for ...
2
votes
1answer
318 views

GraphPlot labels overlapping

If I plot the following graph with an EdgeRenderingFunction, the position of both the labels are at dead center, and with a large graph I have the labels completely ...
0
votes
1answer
49 views

Pruning coordinates in subarrays of a list conditional on them having non-real components

If I have a list of 2D coordinates placed in subarrays of a data structure like the following: ...
2
votes
4answers
2k views

System Modeler can't find g++ in Mac OS X Mavericks

I've just purchased SystemModeler (Mac OS X Mavericks) but can't verify the g++ compiler path. I assume it's in the Xcode package but nothing I've tried seems to work, for example, Applications/...
3
votes
2answers
282 views

Import numeric data into Mathematica

I have a C++ program that outputs a set of numbers at each time step. A blank line separates successive time steps. Here is an example of my data format: ...
1
vote
2answers
659 views

Swapping elements of list

Say I have a directed graph inputted in the following format in Mathematica: g = {{1, "a", 2}, {2, "b", 1}} I'd like to plot this graph using ...
1
vote
2answers
144 views

Quickly pruning elements in one structured array that exist in a separate unordered array

I have two lists, which we'll call testList and modifiedTestList. The first list looks something like this: ...
8
votes
1answer
585 views

How can I scale a plot in vector graphic or PDF form?

I am not at all a computer graphics expert, but it seems that portable document format (PDF) files have a "native size," even though they may (and usually do!) contain vector graphics that can be ...
1
vote
0answers
108 views

LinearProgramming errors

I have a family of equations I want to solve over the non-negative integers. One particular instance of it is this. ...
3
votes
1answer
281 views

Multivariate resultant in Mathematica?

Is there any command in Mathematica 7 which can compute the (McCaulay) resultant of a parametric system of multivariate polynomial equations? In fact, it would be great if there is also a way to ...
3
votes
3answers
149 views

Find $Y \in (0, 5)$ such that the roots of $4x^2 + 4xY + Y + 2 = 0$ are real?

The problem is to find all $Y \in (0, 5)$ such that the roots of $4x^2 + 4xY + Y + 2 = 0$ are real. I took a straightforward approach with Mathematica with the intent of listing the only solutions ...
3
votes
2answers
248 views

Variable length list with # and [[i]] as elements

I need to create a list that as an input receives the number $N$ of elements that it will contain and that returns: ...
3
votes
2answers
347 views

Selecting for 2D points that are within a threshold distance of an upper- and lower-bound number of points

I have a very large set of 2D points: numberOf2DPoints = 10^6; pointList = RandomReal[{0, 1000}, {numberOf2DPoints, 2}]; I'd like to find a way to quickly ...
5
votes
1answer
277 views

Finding an optimal overlay of two point clouds

Imagine I have two sets of points: ...
1
vote
1answer
2k views

Animate curve parametric plot on a surface

I have a surface s = Plot3D[{x,y,F[x,y]},{x,-1,1},{y,-1,1}] with $F$ predefined, and a curve ...
0
votes
1answer
2k views

DSolve to solve a system of differential equations [duplicate]

I need to solve a system of differential equations as follows: ...
2
votes
3answers
150 views

Incorrect behaviour of Locator inside Show?

Why doesn't Locator behave correctly in the following code? ...
1
vote
1answer
224 views

Passing a joined list of symbols for Module or Block to treat as its own local symbols

The Question I'd like to write a function which itself takes a list of symbols, e.g. Foo[{x, y, z}] to pass to Module within,...
6
votes
2answers
1k views

Plotting: Is anyone familiar with gradientfieldplot command?

I am trying to plot this graph showing the electric field lines and lines of equipotential based off the electrode configuration(in black) of two parallel lines. This is what I've been using for other ...
35
votes
7answers
1k views

Nice formatting for the results of a dice game simulation

One of my Mathematica interests is in problems related to the formatting of output. Getting nice formatting from Mathematica is often frustrating, but occasionally Mathematica will delight me by ...
4
votes
2answers
209 views

Finding the characteristic function of a TransformedDistribution[]

I am trying to find the characteristic function of a sum of "named" distributions, though I am interested in how to use Mathematica to find the characteristic function of $$f(X_1,\ldots, X_n),$$ where ...
2
votes
1answer
417 views

How do I label contour lines that are superimposed on a 3d plot?

I need to generate a 3D plot of a function, say $z = \sin(x)\cos(y)$, with contour lines drawn at specified intervals. I also want to label each contour line with its $z$-value. I have discovered how ...
5
votes
1answer
324 views

ListDensityPlot crashes the kernel

ListDensityPlot[ Flatten[Table[{i, j, Sin[i + j]}, {i, 1, 20}, {j, 1, 20}], 1]] gives the expected result, but a linear scale crashes my kernel (please save your ...
6
votes
1answer
848 views

Is there anything like a C pointer (or returning a reference) in $Mathematica$?

I want to do in Mathematica what the following does in C. ...
5
votes
0answers
100 views

Using quantifiers with free indices as declarative conditions in equation solving

This is a toy example: Is there a way to rewrite Reduce[{Norm@{c[1], c[2], c[3]} == 1, 0 <= c[1] < c[2] < c[3]}, {c[1], c[2], c[3]}] ...
2
votes
2answers
311 views

How to restore default seed generation in SeedRandom[] when specifying method?

I want to generate low-discrepancy sequences and for that purpose I use SeedRandom[], like: ...
6
votes
0answers
130 views

Slow NIntegrate over complicated domains (sometimes)

This is no longer a problem with Mathematica 10.* where I can use regions to do the integrations Overview I have a very large matrix I need to calculate where each element requires the integration ...
1
vote
1answer
162 views

Reading between blank lines in external data files

I have an external data file with several columns and thousands lines of data. For the sake of this question, let's assume that we use ...
10
votes
2answers
439 views

How to draw the image of a circle under the action of a transformation of the phase flow?

How to draw the image of a circle $x^2+(y-1)^2<1/4$ under the action of a transformation of the phase flow for the equation $\dot{x}=y,\ \dot{y}=-\sin x$? Here $\dot{x}$ means $dx/dt$. Any help or ...
4
votes
5answers
299 views

Can I generate a “piecewise” list from a list in a fast and elegant way?

Suppose we have a number list a: n = 1000000; a = RandomReal[{0, 1}, {n}]; We want to generate a list ...
2
votes
1answer
193 views

Defining and evaluating new continuous distributions based on Mathematica's distributions

A number of functions operate with Mathematica's set of distributions e.g. Through[{Mean, StandardDeviation, Variance}[UniformDistribution[{umin,umax}]]] which ...
6
votes
1answer
523 views

How to express an expression with only ArcTan and ArcTanh?

I have an expression which is simply (j/k) x^(j/k) LerchPhi[x,1,j/k)] where 0 < j < k. Manually I have been able (...
3
votes
3answers
111 views

Operations on expressions within Hold [duplicate]

I want to convert {Hold[1 + 2], Hold[3 + 4], Hold[5*6]} into Hold[{1 + 2, 3 + 4, 5*6}]. I have tried ...
4
votes
1answer
122 views

How to release $Mathematica$ from the $Pre HoldAllComplete lock

Not sure if posted before, but I'm asking this question from a Mathematica fellow user who tried to load expressions, whose problem soon turned into a prison break game featuring the following code. <...
3
votes
0answers
148 views
4
votes
2answers
163 views

Permutations: selecting reviewers without conflicts of interest

I would like to automate the process of selecting a number of proposal reviewers that fit a conflict of interest criterion. Let's say I have 5 reviewers and 5 applicants from 5 departments. The ...
4
votes
0answers
220 views

Using FindFit to fit nonlinear ODE parameters, subject to a constraint (an inverse problem) [duplicate]

Similar to this post I am finding that constraints tend to make FindFit poor at finding a good fit. However, unlike the previous post, the constraints are required ...
1
vote
0answers
44 views

Matching Root[…] objects with patterns, unexpected hidden argument

I needed to write patterns that could distinguish between arbitrary-function and polynomial forms of Root objects, for example, ...
12
votes
4answers
5k views

Removing empty sets from lists

If I had a list, say, names= {"Andy", "Bob", "Carly", "Sandy", "Jeff", "Tim", "Tom", "Zach"} and I decide to pick a characteristic only a certain of them have, ...
2
votes
0answers
72 views

The “right” way to define a custom Encoding format?

I have implemented an Import|Export format for xz that behaves like gzip and other encoding formats: ...
0
votes
1answer
380 views

How do you find the longest sublist within a nested list

Say, I have a list stuff={{eat,tea,now},{how,did,you,say},{the,cat,ate,was,can},{win,din,sin}} I have a nested list and I want to find the list that has the most ...
2
votes
0answers
152 views

Is it possible to use Gaussian cgs units in $Mathematica$ computations?

I was trying to do computations in Gaussian cgs units, and of course I failed due to dimensional issues. For instance, $q_1 q_2/r$ cannot be converted to $\mathrm{erg}$ since Gaussian system uses $4\...
1
vote
2answers
2k views

Create simple table with function of column values

I just want to create a simple table: Three input columns, one output column Call the inputs {x,y,z}, each can take values ...
1
vote
1answer
992 views

Change font for the whole notebook

Is there any option Mathematica's preferences to change the font for the whole notebook? I know how to change the font of individual cells.
2
votes
2answers
211 views

Plot: how to have the y-range automatically scale to min-max on the x-range?

I have a long list of {date,value}. I would like to use DateListPlot to plot only a subrange, from date1 to date2, with the range on the y-axis automatically chosen to be between the min and max ...
17
votes
3answers
392 views

How to efficiently find moments of a multinormal distribution?

Update: Starting from V10.0 the build-in Moment is fast enough for practical use. I have a multinormal distribution with covariance matrix $\sigma$ and zero mean....

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