# All Questions

151k views

### xkcd-style graphs

I received an email to which I wanted to respond with a xkcd-style graph, but I couldn't manage it. Everything I drew looked perfect, and I don't have enough command over ...
3k views

### Metaprogramming in Mathematica

Being functional, and having no "quotation", i.e. essentially treating data and programs semantically same, Mathematica seems naturally capable of doing metaprogramming. But could anyone construct a ...
3k views

### Minimal effort method for integrating C++ functions into Mathematica

As of Mathematica 8, what is the minimal effort way to integrate an existing C++ function into Mathematica? I think we have these: MathLink (it was quite long ago I used it last time) communication ...
1k views

### Once more on object orientation in Mathematica: does it have to be so hard?

Recently I came across a set of problems which would be solved most easily within an object-oriented approach. I first attempted to solve them by other means, but found the complexity of the code ...
2k views

### How to find circular objects in an image?

How could I use morphological processing to find circular objects in an image? More specifically, I need to detect road signs. I need to get the "80 speed limit" sign from this image:
3k views

### Plotting implicitly-defined space curves

It is known that space curves can either be defined parametrically, \begin{align*}x&=f(t)\\y&=g(t)\\z&=h(t)\end{align*} or as the intersection of two surfaces, ...
947 views

### How to efficiently find positions of duplicates?

Is there an efficient way to find the positions of the duplicates in a list? I would like the positions grouped according to duplicated elements. For instance, given ...
1k views

### Aborting evaluation when the memory exceeds a certain limit

Sometimes when generating a lot of data the memory usage shoots beyond its physical realm and my laptop freezes. There is no way to stop Mathematica when this happens. Task manager (or its equivalent ...
622 views

### Prepend Information to Warning Messages

I have a function running within a Do loop that sometimes issues a warning. I'd like to prepend the warning with the loop ctr so that I can go back and debug that instance later. Basically, I would ...
326 views

### How can I get the unchanged Box form of an arbitrary expression?

One may observe that MakeBoxes does not give the actual Box form of various expressions: MakeBoxes[{1*^4, 000123, a*b c}] ...
1k views

### Open Excel file with Mathematica

I would like to open an Excel file and manipulate it as a COM object. While I'm able to open an instance of excel with ...
663 views

### Elegant manipulation of the variables list

I have a list of global variables (some of them are indexed variables), for example: varsH = Hold[U0[1], U0[2], B0, V0[1], V0[2]] Or (if it is easier to handle) ...
911 views

I have been working on picking expressions apart using Head and Part and encountered a little mystery. Consider the canonical ...
999 views

### Reading periodic elements from a large file

I have a large binary data file (big endian) with 100+ million "rows" of 11 elements, combination of floats and integers. This is the format: ...
1k views

### Generating a broken or snipped axis in ListPlot

I have two data sets, data1 and data2. For example: ...
2k views

### Delete duplicate elements from a list

If a list contains duplicate elements, for example list = {a, 1, 5, 3, 5, x^2, x^2}, how can the duplicate elements be removed? The result would be ...
649 views

### How to perform a depth-first preorder traversal of an expression?

Due to confusion of terminology on my part I asked the wrong question before. Since it has already received other answers I shall not edit it, but instead ask the question I meant to in the first ...
887 views

### How to modify function argument?

Usually in programming languages, function arguments are normal local variables, which can be modified. Is this not true in Mathematica? ...
441 views

### Problem with ContourPlot

I tried these ...
1k views

### Fixed color scale in multiple density plots

I think there should be a simple solution for my current problem, but neither StackOverflow (or the help of Mathematica) or Google have it. I have to plot multiple density plots with a color ...
402 views

### Evaluating an If condition to yield True/False

I would like to decide whether an option passed to my custom function has the value Automatic or something else. This is my attempt: ...
204 views

I don't understand the following: f[a_, b_] := a + b ls = {1, 2, 3}; MapThread[f, {ls, {10, 20, 30}}] This yields ( as expected ) {11,22,33} If I change ...
7k views

### $\LaTeX$ and Mathematica

I quite often would like to draw graphics in my $\LaTeX$ documents using Mathematica. I have encountered three problems. I would like to know if there are any workarounds to these problems I would ...
4k views

### Recovering data points from an image

Unfortunately, some data can only be obtained in picture form (Japanese publications anyone?). Since this cannot be worked with, it has to be converted to a dataset that can; I was wondering whether ...
3k views

### How can I generate this “domain coloring” plot?

I found this plot on Wikipedia: Domain coloring of $\sin(z)$ over $(-\pi,\pi)$ on $x$ and $y$ axes. Brightness indicates absolute magnitude, saturation represents imaginary and real magnitude. ...
4k views

### How to make a 3D globe?

There are many ways to create a 3D Earth that is rotatable (see here, here, related here), but most of them have some drawbacks. These issues mainly stem from either ...
1k views

### How to generally match, unify and merge patterns?

This question was split from this one. While that question is now about how to match two particular patterns (mostly using Verbatim or ...
719 views

### Can a Trie be implemented efficiently?

What is the most space and time efficient way to implement a Trie in Mathematica? Will it be practically faster than what is natively available in appropriate cases?
2k views

### How to change the default ColorData used in Mathematica's Plot?

This question leads on from the recent question What are the standard colors for plots in Mathematica? There it was determined that the default color palette used by ...
1k views

### How to select minimal subsets?

I am a newbie, so please point me in the right direction if you feel this question has been answered somewhere else before. Here goes: Suppose I have a list like this: ...
630 views

What are some complete examples of what one would include in a FrontEnd init.m that would make use of FrontEnd`AddMenuCommands ...
449 views

### Are there guidelines for avoiding the unpacking of a packed array?

Packed arrays are very useful because they save memory and generally allow speedier and more efficient calculation times. If a list of data currently stored as a packed array is unpacked, it can slow ...
900 views

### “Covering up” text in Graphics

Consider the following code: ...
646 views

### Can I simplify an expression into form which uses my own definitions?

This seems like a simple thing to do, but I couldn't find anything relevant from Mathematica documentation. So suppose I have an expression: a*b/(a + a*Cos[a/b]) ...
3k views

### Sizing cells in a GraphicsGrid/GraphicsRow

I would like to add a colour bar to a plot. I tried to use GraphicsRow for this. In a GraphicsRow, each item is given the same ...
1k views

### Can 2D and 3D plots be combined so that the 2D plot is the bottom surface of the 3D plot boundary?

I have a ListlinePlot function, that I would like to combine with both a Graphics3D plot and a ...
1k views

### Assigning values to a list of variable names

As part of a calculation I need to do something like this Evaluate[{aaa, bbb, ccc}[[ index]]] = {1, 2, 3, 4, 5} so if index is ...
407 views

### Usage of Assuming for Integration

For some reason, when I enter the following integration in Mathematica Assuming[{k ∈ Integers}, Integrate[ Exp[ I k t], {t, -π, π}]] the result turns out to be ...
868 views

### Combined numerical minimization and maximization

I want to numerically calculate the maximum of a function defined by the minimization of another function, like the following: ...
884 views

### Mathematica won't give eigenvectors but Wolfram Alpha will? What am I doing wrong?

If I ask Mathematica to find the eigenvectors and eigenvalues of the matrix: ...
707 views

### How Can I use Solve/Reduce Output

Suppose I want x and y to be rationals Solve[ x^2 + y^2 == 1, {x, y}, Rationals] I am ...
437 views

### Retrieving the ImagePadding in absolute units

Consider the following graphic: g = Graphics[Circle[], Frame -> True, FrameLabel -> {"one", "two"}] Retrieving the ...
238 views

In the ideas shared in my answer to this post Struct equivalent in Mathematica? at the end I propose a solution that changes the way Set works in a particular case that can be expressed in plain words ...
804 views

### Why is ContourPlot not displaying this curve?

I am using the general form of a second-degree plane curve: $$Ax^2+2Bxy + Cy^2+2Dx + 2Ey + F = 0$$ I want to randomly generate plane curves of this form, so I am using ...
556 views

### Automatically load packages at startup

I'm a physics student and I try to simplify my day with Mathematica. Every time I use Mathematica I need Div[], Grad[], ...
831 views

### Annoying display truncation of numerical results

I have a lot of data to inspect. An example of a number in my program is 123.189094 This gets displayed as 123.189 ...
908 views

### Using D to find a symbolic derivative

I need to do the following: Define a function Take the derivative of this function and have a look at the symoblic representation Substitute in some values With the bonus that I want to use the ...
258 views

### How can I compare a dynamic variable with a literal in Mathematica?

I'm doing a Mathematica Notebook and I want to make an alarm clock. Something like this: ...