All Questions

12
votes
2answers
521 views

Using Goto and Label in compiled function?

Below I post some rudimentary code to show that there is something wrong using Goto and Label commands in compiled functions (or I believe there is something wrong). It seems that the command Label is ...
12
votes
1answer
303 views

Unexpected behavior from VectorPlot

I am surprised at the behavior of VectorPlot in the following sense: plotting a vector field and examining the output at a point $(x_0,y_0)$ reveals that Mathematica doesn't draw the tail of the arrow ...
12
votes
3answers
317 views

What is an efficient way of selecting multiple colors via Manipulate?

Background: The following snippet is what I (intend to) use in a Manipulate form where up to 12 different colors can be selected: ...
12
votes
1answer
182 views

Solve[ ] with Method -> Reduce gives a different result than Reduce[ ]

Why does Solve[Sqrt[x + Sqrt[x]] - Sqrt[x - Sqrt[x]] == m Sqrt[x/(x + Sqrt[x])], x, Reals, Method -> Reduce] give a different result than ...
11
votes
2answers
464 views

Phase portrait on a cylinder

It is very nice and very easy to make a sketch of a phase portrait with StreamPlot. For example, for the classical pendulum, defined by $$ \dot x=y,\\ \dot y=-\sin x, $$ The code ...
11
votes
1answer
183 views

Unwanted PlotMarkers appear at non-existent places

In this simple code ...
11
votes
3answers
190 views

How to collect expressions from cells created by Print?

I have a notebook where evaluation of a certain cell produced hundreds of adjacent output cells using Print. I need to create a list containing all expressions from ...
11
votes
4answers
650 views

List comprehension in Mathematica

Python supports a concept called "list comprehensions". Following is sample example ...
11
votes
3answers
233 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 ...
11
votes
1answer
188 views

How to find longest monotonic sequence?

I have a list, for example list = {2, 1, 3, 5, 4, 6} How to find longest ascending sequence of this list? There are two meanings of this question: Find the ...
11
votes
1answer
432 views

RLink and R v3.0.1?

Running InstallR["RHomeLocation" -> "C:\\Program Files\\R\\R-3.0.1"] results in a popup box titled "Version Mismatch" saying Error: R.DLL version does ...
11
votes
1answer
277 views

Overloading second argument of CountryData

For convenience I'm trying to add an extra property to CountryData ...
11
votes
4answers
651 views

Second level depth pure function?

I have the following working construction: Select[ln125, # == Nearest[ln125, 551.748][[1]] &] Here, ln125 is a one ...
11
votes
5answers
257 views

Construct an infix operation from a list

Inspired by this question, if I have a list {a, p, b, q, c} where p and q are binary ...
11
votes
3answers
904 views

Derivatives (divergence, gradient, curl) of interpolated 3D data

How can I calculate a vector derivative (i.e. divergence, gradient, curl) of interpolated data? For sample data, you can use: ...
11
votes
3answers
174 views

Emulating Sequence with my own function

I just considered if/how one could implement Sequence in Mathematica if it were not predefined. It turned out that the following simple definition has in all my ...
11
votes
2answers
597 views

Google Code Jam: Mountain View code review

After participating in Google Code Jam 2012 Round 2, it occurred to me that the Mountain View problem boiled down to solving a set of linear inequalities, which could be done in Mathematica. I've only ...
11
votes
7answers
326 views

Question about evaluation control

I want to make a function that takes a function as a parameter and prints an integral with the function inside. I've tried this: ...
11
votes
1answer
1k views

How to export transparent raster plots?

Is there an easy way to get transparent plots that work with Save Graphic As using a compatible file format such as GIF or PNG? I tried ...
11
votes
3answers
257 views

Numbers in alternate bases transcend the evaluator?

It looks to me like a number in a base other than base 10 gets evaluated before the evaluator ever gets a chance to be tweaked. For example, FullForm[16^^abcdef] ...
11
votes
4answers
712 views

How do I get rid of the overlap of gridlines and tick mark labels?

I wish to include the plot generated by the following Mathematica code ...
11
votes
3answers
2k views

Poor rendering of fractals

Could someone explain why I get those ugly graphics .. ..trying to use fractals in mathematica 8 ? I'd also like to know if it is possible to draw 2D fractals in Mathematica My configuration ...
10
votes
2answers
174 views

How to restore function attributes to default

Adding an attribute to a function is easy and clearing attribute is easy also. But I don't know really how to restore the attributes of a function to its defaults. All I do is quit the kernel or close ...
10
votes
5answers
812 views

The mysterious gap inside Grid

There's this gap inside Grid which I cannot seem to remove. Perhaps someone knows how. ...
10
votes
4answers
263 views

No response to an infinite limit

Trying to compute this limit, things seem to get frozen, even for hours. What would you recommend to fastly compute it? ...
10
votes
1answer
460 views

How do I place a texture on an irregular 3D model?

I'm trying to reproduce a textured head in Mathematica, and I'm using a kind of 'net' of a head which contains all the features on the face. The texture looks like this: which is supposed to look ...
10
votes
1answer
206 views

Is there a method to enumerate the keys/values of System`Utilities`HashTable

Lacking from the simple API of System`Utilities`HashTable is a method to enumerate the keys/values. ...
10
votes
2answers
361 views

How can I access the internal function that plots a molecule from a formatted XYZ file?

Mathematica has the ability to plot a molecule using the data contained in an XYZ file. This is a simple text file, of which this is an example. The molecule is plotted using the Import command. ...
10
votes
1answer
384 views

How to make a volume CUDA rendering isometric?

I just realized that the output of CUDAVolumetricRender[] uses (quite marked) perspective, which I do not want (for scientific data representation, it can be very ...
10
votes
1answer
631 views

NDSolve Differential Equation Error

I am trying to solve the following differential equation- ...
10
votes
1answer
202 views

Unexpected result from Flatten

Consider the following three evaluations involving Flatten: Flatten[f[f[f[x, y], 1, 2], f[x, y]], Infinity, f] f[x, y, 1, ...
10
votes
1answer
191 views

Why do DateList, DateString, and AstronomicalData ignore $TimeZone?

My reading of the documentation for DateList and DateString lead me to believe that both functions use ...
10
votes
5answers
781 views

Implementing CGS unit system in Mathematica 9

So I've just installed the trial version of Mathematica 9. The first noticeable feature for me is the new built-in physical units. I used AutomaticUnits package ...
10
votes
2answers
348 views

Determining the default Method used in optimization and root-finding algorithms

Is it possible to extract the Method which is used in functions like NMinimize, FindRoot, ...
10
votes
3answers
524 views

Mathematica Plot: Inconsistency when plotting large values

I am working with a function in Mathematica and I am getting some inconsistencies when I plot it. As I really need to understand were this comes from I would appreciate any help. I am working with a ...
10
votes
2answers
399 views

Animation: presenting events that persist in time

I have a list of events that occurred on specific moments in time. In the example below, the three events occurred at 23:09, 23:13 and 23:17. I was able to build an animation that flows from time ...
10
votes
4answers
1k views

How do I plot Thomae's function in Mathematica?

I wanted to plot this function $$f(x) =\begin{cases} 1 & \text{if } x= 0 \\ \tfrac1{q} & \text{if } x = \tfrac{p}{q}\\ 0 & \text{if } x \in \mathbb{R}-\mathbb{Q} ...
10
votes
2answers
169 views

Subtle difference in conditional rules placement

I had gotten used to thinking of the placement of a condition in a rule definition as logically immaterial. In my specific example, namely ...
10
votes
4answers
714 views

Efficiently Visualising Very Large Data Sets (without running out of memory)

I have put a few really hard problems in combinatorics up against Mathematica 8. I'd have to say that it works really well, until you want to view the data. If you look at my question Advanced ...
10
votes
1answer
479 views

How to import date (YYYY-MM-DD) data from a file?

I have a file with data in form {date, value}: 2010-05-19 17 2010-05-20 20 ...
9
votes
1answer
125 views

Tracking Initialization

How to track Initialization step by step? Any tricky solution is ok. One condition, x should be ...
9
votes
2answers
168 views

Extracting values with multiple keys

I want to extract sorted data from a huge database based upon two (or more) keys in a very timely manner. Here is a reproducible toy example for two keys only: ...
9
votes
2answers
1k views

Why is this semicolon in red?

I have a piece of code that works well, but when I put a semicolon after a plotting statement, the semicolon appears in red. What's the error?
9
votes
1answer
378 views

What is the proper way to verify that two expressions are equivalent?

First of all, it appears to me that $$\left|\frac{1}{x} + x^2\right| \Leftrightarrow \frac{|1 + x^3|}{|x|}$$ is true. I don't know why, but my attempt to verify it in Mathematica failed. ...
9
votes
2answers
316 views

Recursive Integral for Volume of $n$-Ball

The volume of an $n$-ball (the $(n+1)$-dimensional analogue of a disk) of radius $r$ can be found by the following integral recurrence: $$V_0(r)=2r$$ ...
9
votes
5answers
363 views

Count consecutive occurrences in a list above a certain value

I am trying to tally and sort the number of consecutive occurrences in a list above a certain value. For instance: ...
9
votes
1answer
127 views

What are the scoping rules for function parameters shadowing System` symbols?

Here are some very contrived code snippets, highly unlikely to appear in real code, but still I am curious why they behave like this: ...
9
votes
3answers
391 views

FindShortestTour for charity (or: How can I optimize meal delivery with FindShortestTour?)

I've been wondering about this for a while - but never got around to asking - until I saw faleichik's incredible answer to Mathematica Minecraft. I did some work at a not-for-profit a little while ...
9
votes
1answer
418 views

FourierSeries for rational function looks wrong

I have the following code: ser[x_] = FourierSeries[(\[Pi]^2 + a)/(3 x^2 + a), x, 10] // N // Chop It gives me some series, which I then try to plot. And ...
9
votes
2answers
269 views

Determining whether two $k$-chromatic graphs are isomorphic (respecting vertex coloration)

Consider the case where I have two $k$-chromatic graphs $G_1$ and $G_2$, i.e. two graphs where individual vertices can be colored with one of a set of $k$ total colors, and I would like to determine ...

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