23
votes
3answers
2k 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: ...
18
votes
3answers
495 views

What are the requirements for a well behaved indexed variable? Subscript, ToExpression, Downvalue?

On writing this answer I needed to call a function, (NonlinearModelFit) with an unknown number of parameters. We have learned that we should not use ...
22
votes
1answer
620 views

Shorter syntax for Fold and FoldList?

I find it tedious to write out the following: a = {1, 2, 3, 4}; Fold[f, First @ a, Rest @ a] f[f[f[1, 2], 3], 4] It ...
19
votes
3answers
2k views

Removing unwanted appearance of underlying mesh

Let us first define two positive definite matrices: M1 = {{2, -6}, {4, 8}}; M2 = {{2, 3}, {4, 8}}; then set two points ...
15
votes
8answers
1k views

How to Map a subset of list elements to a function?

How would you, given a list {1, 2, 3, 4}, apply a function f to 1 and ...
11
votes
4answers
2k views

Extracting variables from an expression

I'm looking for a way to extract a list of variables from an expression, for example with an input like: ...
11
votes
3answers
1k views

PolarPlot render oddities

I apologize if this is a obvious question and answer, I don't often use Mathematica to display plots or graphics in general to be honest. So, I was tutoring my cousin yesterday in relation to Polar ...
28
votes
2answers
2k views

Meaning of backtick in floating-point literal

If I compute, say, 1/3//N, Mathematica displays 0.333333 as the result. When I copy that output to use elsewhere, the paste ...
19
votes
1answer
551 views

Using Evaluate and Evaluated -> True in Plot

A few use cases: (1) This, as expected, returns (almost) immediately: f[x_?NumericQ] := Evaluate[(Pause[1]; x)] Plot[f[x], {x, 0, 1}] (2) This takes ...
13
votes
1answer
2k views

Plot showing discontinuity where it shouldn't

I was trying to integrate a continuous function with a kink and I did it two ways and both ways the plot of the result shows a discontinuity. I also later want to differentiate the Integrated ...
3
votes
3answers
582 views

Help on evaluation control?

I want to plot series of slopes: x, 2x, 3x, 4x, 5x, 6x... I'm trying to do this: ...
109
votes
3answers
6k views

How to make use of Associations?

I have been curious about it for long. Now that Mathematica 10 arrives, I think it's time to ask the question: How the new Association data structure would be used ...
62
votes
2answers
3k views

Profiling from Mathematica

I've always wished I could do some profiling like you get in Wolfram Workbench, but directly from Mathematica, without using or having Workbench. If it is possible, how can I do it?
43
votes
2answers
2k views

Sketch-type graphics with transparency and dashed hidden lines?

I'd like to create transparent graphs like the following from P1095, Calculus 6th Ed, by James Stewart. Can Mathematica accomplish this? By "transparent," I mean the ability to see the interior, ...
50
votes
6answers
4k 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 ...
37
votes
4answers
2k views

Compiling more functions that don't call MainEvaluate

I would like to use Compile with functions defined outside Compile. For example if I have the two basic functions ...
55
votes
1answer
1k views

Incompatible Changes since Mathematica Version 7?

There is documentation of the incompatible changes made to Mathematica with each major release: Incompatible Changes since Mathematica Version 1 Unfortunately that documentation simply stopped ...
36
votes
6answers
3k views

How to plot ternary density plots?

How can I get a ternary density plot just like the plots from OriginLab? ContourPlot and DensityPlot seemingly can accept the ...
33
votes
3answers
2k views

Changing Values in an Association using Map

I am trying to change the value of one key in an association based on the value of another key in that association. So if my association starts as: ...
31
votes
2answers
2k views

Specific initial sample points for 3D plots

PlotPoints lets you determine how many sample points you want in each direction, but sometimes I want specific ones. For Plot ...
39
votes
2answers
1k views

Why is the new PositionIndex horribly slow?

This issue has largely been mitigated in 10.0.1. New timings for the final test below are: ...
22
votes
4answers
925 views

Resource management in Mathematica

I am using a library that has functions like createSomeObject[] and deleteSomeObject[obj]. It is an interface to a C language ...
21
votes
4answers
4k views

How to get intersection values from a parametric graph?

I have this graphed: ParametricPlot[{2.4*Cos[t] + 1.6*Cos[3 t/2], 2.4*Sin[t] - 1.6 Sin[3 t/2]}, {t, 0, 4*Pi}] It is a star, and the lines cross each other ...
27
votes
3answers
2k views

“Covering up” text in Graphics

Consider the following code: ...
24
votes
1answer
1k views

Analogue for Maple's dchange - change of variables in differential expressions

Maple owns an interesting function called dchange which can change the variables of differential equations, but there seems to be no such function in Mathematica. ...
21
votes
2answers
793 views

How to inject an evaluated expression into a held expression? [duplicate]

I know that there are methods to structurally manipulate held expressions (discussed e.g. here), but I failed to apply those for this particular problem: ...
18
votes
2answers
2k views

How do I automatically evaluate a cell when a notebook is opened?

I'm trying to put together a GUI in Mathematica and need to evaluate one cell to kick that off. Is there a way to automatically evaluate that cell when the notebook is opened? Here is an example of ...
25
votes
2answers
5k views

How to enter matrices in block matrix format?

Example: I have a matrix $R = \left( \begin{array}{cc} A & \mathbf{t} \\ 0 & 1 \end{array} \right) $ where $A$ is 3-by-3 and $\mathbf{t}$ is 3 by 1. Or in Mathematica ...
20
votes
5answers
2k views

How to pass a symbol name to a function with any of the Hold attributes?

Given a function with the attribute HoldFirst, HoldAll or similar, and a variable, list, how ...
13
votes
2answers
11k views

What does # mean in Mathematica?

I asked Mathematica to compute the following Solve[c (1-x)^2-x^(1/4) == 0, x] and it returned this: x = Root[#1^8 c^4 - 8 #1^7 c^4 + 28 #1^6 c^4 - 56 #1^5 ...
29
votes
2answers
1k views

How does Plot work?

I considered the following function: sin[x_] := Module[{}, Print["x=", x]; Sin[x] ] in Mathematica. Next, I tried to plot it using: ...
18
votes
2answers
544 views

Where can I get detailed information on how the Plot command works?

The command Plot[x^2, {x, -3, 3}, PlotStyle -> Arrowheads[{-.025, .025}]] /.Line -> Arrow produces this output. What I don't understand is what ...
18
votes
3answers
462 views

What does None mean in a control specification for Manipulate?

I am now struggling to understand code that contains the following (simplified) Manipulate structure. ...
6
votes
5answers
3k 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 ...
27
votes
2answers
868 views

Block attributes of Equal

I answered “Equating matrices (or higher order tensors) element-wise” with: ...
26
votes
1answer
10k views

How to remove redundant {} from a nested list of lists?

There are numerous examples here, whose end result is the removal of empty brackets {} and empty lists. I still can't find an example of simply removing redundant ...
18
votes
2answers
2k views

Basins of Attraction

How does one shade the basin(s) of attraction of a phase plot in Mathematica? I have been trying to do this using the system $$\begin{align*} \dot x &= y\\ \dot y &= -9\sin(x) - 0.20y ...
14
votes
6answers
2k views

How do I obtain the enclosed area of this particular parametric plot?

I'm trying to find a way to obtain the enclosed area of this particular plot. Can someone show me how? ...
17
votes
1answer
910 views

How to put terms in lexicographic order?

Is it possible to have terms like f[w-c] be formatted like this and not like f[-c + w]. I use Mathematica (7.0) for simplifying ...
14
votes
2answers
994 views

Extracting the function from InterpolatingFunction object

I've used Interpolation[] to generate an InterpolatingFunction object from a list of integers. ...
6
votes
5answers
1k views

sliding a tangent line along a curve

I am confused by Dynamic. I am trying to slide a tangent line along a curve, without using DynamicModule, so that I can include ...
13
votes
3answers
2k 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 ...
10
votes
2answers
8k views

How can I plot implicit equations?

If you enter the following into Wolfram | Alpha, you get nice graphs: graph 4 x^4 + y^2 = 2 How do you do this in Mathmatica? I realize that these are not ...
19
votes
5answers
3k views

The difference between 0. and 0

I have a function for which 0 is a special case: f[A___, 0, B___] := 0 But since I am doing numerics, sometimes in the course ...
8
votes
2answers
942 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: ...
8
votes
2answers
2k 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 ...
105
votes
4answers
10k views

Resources for beautiful Mathematica Stylesheets

When the Wolfram Demonstrations were introduced and the Documentation-Center was redesigned, I remember it was the first time I thought someone had put some effort into creating a beautiful ...
35
votes
5answers
12k views

How to use Mathematica functions in Python programs?

I'd like to know how can I call Mathematica functions from Python. I appreciate a example, for example, using the Mathematica function Prime. I had search about MathLink but how to use it in Python ...
49
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 ...
41
votes
3answers
2k 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 ...

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