16
votes
5answers
1k views

Having the derivative be an operator

How do I create an operator which acts like a derivative to everything to the right of it: for example: $ \left( \partial_x + \partial_y + z \right ) x \psi $ How do I make that evaluate to: $x ...
9
votes
3answers
587 views

Problem with ParametricPlot

I'm ploting gear curves (http://mathworld.wolfram.com/GearCurve.html), and I observe that for some parameter values ParametricPlot[] does not plot all the teeth: ...
8
votes
1answer
632 views

What is the difference between Set and SetDelayed?

I have a problem with defining a function and most of time I get confused by Set or = and ...
16
votes
5answers
569 views

Is this the most efficient way to round approximate integers to integers while leaving other Reals untouched?

This might seem like an overly simple question, but I need to specify custom plot tick marks as integers (no trailing decimal point) if they are approximately integers, but not if they are not. Using ...
4
votes
4answers
5k views

Creating a table/Matrix during a For loop

I have a For loop (with i as a counter), which calculates different values (y1, ...
9
votes
6answers
334 views

List-operations only when restrictions are fulfilled (Part 1)

Consider the following: ...
7
votes
3answers
927 views

Finding the number of solutions to a diophantine equation

I want to count total number of the natural solutions (different from 0) of the equation $2x + 3y + z = 100$, but don't know how. How can I calculate it using Mathematica? I tried: ...
6
votes
2answers
381 views

Filling global arrays in parallel calculations

I want to parallelize heavy computations which has to be done many times, the result should be arrays of data. Each calculation does not depend on others (but uses the same variables though). The ...
5
votes
2answers
493 views

Solve an equation in $\mathbb{R}^+$

How can I solve this equation (both numerically and literally) only in the positive reals $\mathbb{R}^+$? Solve[x == (v0 - (A CD t v0^2 ρ)/(4m)) Cos[θ] t, t] And ...
7
votes
2answers
801 views

Create complicated text formulas in graphics

I want to put somewhat complicated, or at least non-standardly formatted, text on some of my graphics. For example, I'd like to be able to use f^[4](x) (where the ...
108
votes
1answer
3k views

Implementing efficient multiple undo

The Mathematica Front End's built-in Undo command can only undo a single editing step. Has anyone implemented or seen implemented an efficient and comfortable multiple undo? I have in mind ideas ...
31
votes
5answers
3k views

How can I extract data points from a black and white image?

Consider the following graph (source): Is there any way to extract the data points from this image in a semi-automatic way? I have seen, and tried the methods suggested in this question, but they ...
46
votes
4answers
1k views
37
votes
6answers
2k views

Does Mathematica have advanced indexing?

I have two $M \times K$ arrays $L, T$ where I would like to set all the elements in $L$ to zero whenever the corresponding element of $T$ is greater than 15. The ...
42
votes
1answer
2k views

Implementing a first person view of 3D objects in a scene

I've created the following scene with a Chinese-style building surrounded by trees, and a horse and a rabbit grazing on the grass in Mathematica (don't ask me why there's a bust of Beethoven in ...
28
votes
8answers
3k views

Circuit drawing in Mathematica

This past semester I taught an introductory electromagnetism course and had quite a nice time using Mathematica to draw all sorts of figures and diagrams (mostly for problems and etc.). However, I was ...
24
votes
1answer
721 views

Linking FORTRAN with Librarylink

FORTRAN code can be called using MathLink or .NET/Link (see the link for a worked examples). But as mentioned in a talk by T.Gayley and J.Klein in Wolfram Technology Conference 2011, LibraryLink, ...
20
votes
2answers
1k views

Debugging memory leaks

I've written my incredibly complex, incredibly elegant analysis function, that works great on small test data. But when I run it on my real (bigger) data set it keeps running out of memory. It turns ...
31
votes
3answers
1k views

How to distribute proprietary Mathematica code

If I want to make package-code completely unreadable, in a way that the end-user can only call my functions, but has no way to re-engineer my definitions, how would I do that? I know I can use ...
32
votes
3answers
2k views

How to find out which method Mathematica selected?

There are commands like NonlinearModelFit[] or NDSolve[] that have the option Method it ...
27
votes
12answers
1k views

Map a function across a list conditionally

It seems that this is a really basic question, and I feel that the answer should be obvious to me. However, I am not seeing. Can you please help me? Thanks. Suppose I have a list of data ...
31
votes
5answers
568 views

Placement of Condition /; expressions

It is my practice to place Condition expressions on the left side of := and :> in almost ...
32
votes
6answers
1k views

Find zero crossing in a list

I'm looking for a function that finds the index of the zero-crossing points of a list. Before I go making my own subroutine to do this, I was wondering if anyone knows of any built-in Mathematica ...
25
votes
5answers
2k views

Are there any cases when For[] loops are reasonable?

To my mind the only reason for the existence of For[] loops in Mathematica is to allow new users with some experience in procedural programming languages to write ...
23
votes
3answers
1k views

How to read data file quickly?

I have a tab separated value file with 10 million rows each of which has three tab separated values. The first value is a string, the second an integer, and the third another string. How to read ...
31
votes
5answers
691 views

Items known by CurrentValue

CurrentValue can be used to poll the state of numerous system values such as the mouse position. Its help page doesn't list all possible items, though. An item like ...
23
votes
2answers
963 views

An efficient circular arc primitive for Graphics3D

As many people have noted, the 2D graphics primitive Circle doesn't work in a Graphics3D environment. Several solutions to this ...
18
votes
3answers
1k views

Generating graphs interactively (GUI)

I want to create graphs interactively using a GUI. I thought of using a ClickPane[] environment. The code I have (in part borrowed from the Documentation) works ...
25
votes
6answers
2k views

Efficient way to generate random points with a predefined lower bound on their pairwise Euclidean distance

Using Mathematica what is an efficient way to generate a list of $n$ random two dimensional points $\{x_i,y_i\}$ where $i=1,...,n$ so that no two points $p_1$ and $p_2$ in the list has an Euclidean ...
18
votes
3answers
1k views

Efficiently determining if 3D points are within a surface composed of polygons

This is the 2nd part of a previous question which I edited to make into 2 separate questions: Extracting polygons from 3D contour plot surface As an extension of my earlier question involving simple ...
23
votes
4answers
852 views

What tools can help in realizing tail recursion?

I had nice discussions with Leonid and Rojo that got me interested in tail recursion. Tail recursion is not always easy to realize with Mathematica, so it would be nice to have some tools to help with ...
20
votes
7answers
3k views

Changing the background color of a framed plot

I frequently generate framed plots like this: Plot[Sin[x], {x, 0, 2 \[Pi]}, Frame -> True] Is there an easy way to change the background color of the framed ...
18
votes
3answers
3k views

Plotting a set of trajectories (not a vector field) in 3D

Consider a set of trajectories in 3D space, that possibly converge. By visualizing trajectories as arrows the result will look crowded as each arrowhead will be placed where the attractor is. In 2D, ...
17
votes
4answers
835 views

Scale Insetted Characters to Plot

I am trying to place a curly brace within a plot such that the top/bottom of the curly brace line up with two horizontal lines in the plot: I have not been able to find a way to make the curly ...
21
votes
4answers
1k views

Sort lists according to the order of another

I have three parallel lists (i.e. the elements in position i of each list are related). I want to sort the first list using the function Sort and make the same changes to the other lists so that I ...
18
votes
3answers
1k views

Fastest way to calculate matrix of pairwise distances

It is a very common problem that given a distance function $d(p_1,p_2)$ and a set of points pts, we need to construct a matrix ...
16
votes
4answers
967 views

How to speed up the function DelaunayTriangulation?

First define a function meshGrid to generate some points: ...
15
votes
3answers
550 views

How to get the real PlotRange using AbsoluteOptions?

The problem in general involves the unreliable behaviour of AbsoluteOptions when option values are implicitly specified (e.g. ...
15
votes
6answers
1k views

Insert $+$, $-$, $\times$, $/$, $($, $)$ into $123456789$ to make it equal to $100$

Looks like a question for pupils, right? In fact if the available math symbol is limited to $+$, $-$, $\times$, $/$ then it's easy to solve: ...
15
votes
6answers
3k views

About multi-root search in Mathematica for transcendental equations

I have some questions for multiroot search for transcendental equations. Is there any clever solution to find all the roots for a transcendental equation in a specific range? Perhaps ...
25
votes
2answers
453 views

Why does Simplify ignore an assumption?

Here is the example: Simplify[x + y, x + y == a] Simplify[x + y, x + y == 5] Mathematica 9 output: x+y 5 I expect the ...
22
votes
3answers
867 views

How to place an image inside a notebook, with the minimum memory footprint?

When creating a notebook with images, like photos, the file tends to quickly get big, which makes it difficult to use the notebook format for training material containing a lot of images. Are there ...
20
votes
1answer
509 views

How do you set attributes on SubValues?

SubValues, as discussed in a previous question, are declared as follows ...
18
votes
2answers
426 views

Implementing a safe ValueQ that does not evaluate its argument

Mathematica has a built-in function ValueQ. Quoting the docs, ValueQ[expr] gives True if ...
16
votes
4answers
764 views

How to collect result continuously (interruptible calculation) when running parallel calculations?

This is the most common pattern to compute a table of results: Table[function[p], {p, parameters}] (regardless of how it's implemented, it could be a ...
14
votes
3answers
870 views

Extracting the coordinate of a particular point of interest from a ListPlot

Is there a way to obtain the coordinate of a point of interest in a ListPlot? As an example, I have a list containing many sets of 2D coordinates and the plot ...
13
votes
2answers
538 views

Question about designing a particular data structure

Background: I store polygons with a color assigned at the face level. In some occasions I want to use vertex colors but I want to store data efficiently, i.e. don't want to duplicate data to the ...
12
votes
3answers
1k views

I'd like to display field lines for a point charge in 3 dimensions

I'd like to display field lines for a point charge in 3 dimensions. Not a force field (short arrows) but continuous field lines that start on the charge.
21
votes
4answers
2k views

Is it possible to prerender animation in Wolfram Mathematica?

I have a DensityPlot which is evaluated for a long time. I wish to use it with animation, but it is absolutely inapropriate. Is it possible to render animation ...
15
votes
4answers
1k views

Real Size Image Printing

I am generating a complicated graphics with Mathematica, but with objects of given sizes (e.g. a line of length 1 inch, between two points). I want to make sure that when I export the graphics, e.g. ...

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