Questions tagged [programming]
Questions on writing non-trivial programs in Mathematica. Do not use this tag for questions on plotting/graphics or for questions on doing mathematics with Mathematica, where the focus is more on the math than the program.
517
questions
546
votes
37
answers
129k
views
What are the most common pitfalls awaiting new users?
As you may already know, Mathematica is a wonderful piece of software.
However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ...
598
votes
19
answers
155k
views
Where can I find examples of good Mathematica programming practice?
I consider myself a pretty good Mathematica programmer, but I'm always looking out for ways to either improve my way of doing things in Mathematica, or to see if there's something nifty that I haven't ...
204
votes
3
answers
53k
views
Alternatives to procedural loops and iterating over lists in Mathematica
While there are some cases where a For loop might be reasonable, it's a general mantra – one I subscribe to myself – that "if you are using a ...
- 270k
122
votes
3
answers
9k
views
What is a Mathematica packed array?
A simple sounding question with a few sub questions:
What is the difference between unpacked vs packed array?
Are packed arrays more space efficent, how much so?
Are packed arrays more time ...
- 2,263
92
votes
5
answers
14k
views
What does the construct f[x_] := f[x] = ... mean?
This question mentions "x := x = trickery".
What does defining a function as f[x_] := f[x] = ... do and what is it good for?
- 19.6k
84
votes
9
answers
6k
views
Updating Wagon's FindAllCrossings2D[] function
Stan Wagon's Mathematica in Action (second edition; I haven't read the third edition and I'm hoping to eventually see it), demonstrates a nifty function called ...
- 124k
66
votes
4
answers
6k
views
How do I evaluate only one step of an expression?
I am looking for a simple, robust way to evaluate an expression only one step, and return the result in a held form.
The definition of a single step is ambiguous, and this itself is probably worthy ...
- 270k
133
votes
9
answers
30k
views
Creating Mathematica packages
I'm building a package to help me write packages and their documentation. In this post I explained how to make a package and its documentation. In the answer I provided I describe how to build a very ...
- 6,450
110
votes
4
answers
7k
views
Flatten command: matrix as second argument
One thing I could never wrap my head around is how Flatten works when provided with a matrix as the second argument, and the Mathematica help isn't particularly ...
- 14.9k
56
votes
2
answers
8k
views
Do I have to code each case of this Grid full of plots separately?
I have written some custom functions to draw multi-panel graphs like this one:
It's done by passing a matrix of (custom) plotting functions to a MultiPanelGraph ...
- 34.1k
181
votes
5
answers
18k
views
Performance tuning in Mathematica?
What performance tuning tricks do you use to make a Mathematica application faster? MATLAB has an amazing profiler, but from what I can tell, Mathematica has no similar functionality.
- 2,419
122
votes
7
answers
17k
views
Struct equivalent in Mathematica?
I really miss having something like a struct in Mathematica. I know of (and regularly use) a couple of programming techniques which feel like a ...
- 5,340
89
votes
11
answers
20k
views
How to check if a 2D point is in a polygon?
Background: I use code from An Efficient Test For A Point To Be In A Convex Polygon Wolfram Demonstration to check if a point ( mouse pointer ) is in a ( convex ) polygon. Clearly this code fails for ...
- 9,647
74
votes
3
answers
5k
views
when is f@g not the same as f[g]?
I have always thought that f@g will give the same result as f[g] in all cases, and it is just a matter of style which one to use ...
- 137k
40
votes
4
answers
11k
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?
...
- 2,023
10
votes
2
answers
1k
views
Programming with Dynamic
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 ...
- 9,647
23
votes
4
answers
3k
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) ...
- 61.5k
95
votes
6
answers
4k
views
The clearest way to represent Mathematica's evaluation sequence
WReach has presented here a nice way to represent the Mathematica's evaluation sequence using OpenerView. It is much more clear way to go than using the standard <...
- 61.5k
56
votes
2
answers
3k
views
How do you set attributes on SubValues?
SubValues, as discussed in a previous question, are declared as follows
...
- 33.9k
33
votes
5
answers
2k
views
How to perform a depth-first preorder traversal of an expression?
Mathematica provides functions that perform a depth-first postorder traversal, or which use such a traversal, including: Scan, ...
- 270k
56
votes
5
answers
6k
views
How can I implement dynamic programming for a function with more than one argument?
Dynamic programming is a technique for avoiding the repeated computation of the same values in a recursive program. Each value computed is immediately stored. If the value is needed again, it is not ...
- 124k
5
votes
4
answers
613
views
Expressions containing globally undefined symbols inside a function where they are defined
Consider the following code.
f[a_,b_]:=x
x=a+b;
f[1,2]
(* a + b *)
From a certain viewpoint, one might expect it to return 3 ...
- 167
75
votes
7
answers
5k
views
Functions vs. patterns
Every time I define a new function, I wonder which construct I should use: true functions obtained by using Function, or rule-based syntax. For example, these are ...
- 14.9k
44
votes
4
answers
5k
views
Can a function be made to accept a variable amount of inputs?
I have a function that takes two inputs and processes them for a single output. What I need is one that can take a varying number of inputs. and process them to a single output. Is this possible in ...
- 4,478
43
votes
6
answers
3k
views
45
votes
5
answers
9k
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 ...
- 233k
116
votes
4
answers
5k
views
Programmatic formatting for Mathematica code - possible?
It seems to be both an interesting programming challenge and a very useful practical application to have a Mathematica program which would allow one to pretty-print Mathematica code, so that it is ...
- 114k
36
votes
6
answers
7k
views
Finding all elements within a certain range in a sorted list
Suppose we have a sorted list of values. Let's use list = Sort@RandomReal[1, 1000000]; for this example.
I need a fast function ...
- 233k
46
votes
5
answers
14k
views
ListPlot with each point a different color and a legend bar
I would like to generate a ListPlot with the color for each point in the plot corresponding to a particular value (not associated with the position in the plot). I'...
- 5,340
40
votes
1
answer
1k
views
What can I use as the second argument to Return in my own functions?
Having found out about the second argument to Return I played a bit with it, and the following tests all resulted in ...
- 19.1k
27
votes
2
answers
2k
views
Using a list of tuples in a pure function
I want to use a list of tuples within a function to make assignments.
Say I want to make assignments of the form
value[i,j] = val
What I have is a list of ...
- 13k
156
votes
9
answers
15k
views
General strategies to write big code in Mathematica?
I think after six months of exposure to Mathematica and the Wolfram Language I am fairly OK with writing short codes and snippets. However, what are some general strategies to use in order to write ...
- 8,910
77
votes
4
answers
7k
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 ...
- 114k
113
votes
4
answers
11k
views
What are the recommended settings for git when using with Mathematica projects?
Background
I'm relatively new to git — currently overseeing an offshore .NET-based development project on GitHub within a private business account, but little experience beyond that.
I'd like to set ...
- 2,514
60
votes
5
answers
7k
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 ...
- 12.6k
27
votes
3
answers
3k
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:
...
- 9,572
40
votes
2
answers
3k
views
How to make a curve selectable from a scaned image and convert it to a list of coordinates
I have a scanned image (binary-ized):
Is there any way to reduce one of these curved lines (full or dotted) to a series of its coordinates (e.g., sampling interval of 0.01 on x-axis)?
I've read ...
- 633
83
votes
3
answers
9k
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 ...
- 8,666
56
votes
3
answers
15k
views
How to create a progress bar?
I would like to create a progress bar tool that allows me to see how my computations are going.
I found answers to this question on many sites, I even found a package for it ( http://www.physics.ohio-...
- 563
44
votes
4
answers
2k
views
Is there a convenient way to copy/paste text-interspersed SE code snippets into Mathematica?
Is there a way to copy and paste code snippets from SE to Mathematica if these snippets are interspersed with text?
Like e.g. in Morphing Graphics, color and location in both the question and answer, ...
- 15.3k
38
votes
2
answers
5k
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 ...
29
votes
4
answers
11k
views
How to find numerically all roots of a function in a given range?
It is common that I search numerically for all zeros (roots) of a function in a given range. I have written two simple minded functions that perform this task, and I know of similar functions on this ...
- 7,046
23
votes
2
answers
5k
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 ...
- 4,478
18
votes
2
answers
3k
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
...
- 1,995
96
votes
2
answers
7k
views
What are the best practices / most common / idiomatic ways to report errors in Mathematica?
In particular, what are the best ways to report errors about incorrect arguments to a function? Checking for the correct arguments is relatively easy using patterns, but how to report an informative ...
- 233k
32
votes
2
answers
18k
views
Pass function or formula as function parameter
I can write either
Integrate[x^2, {x,0,3}]
or
f[x_] = x^2
Integrate[f[x],{x,0,3}]
and get the same computation. Suppose I ...
- 4,209
20
votes
5
answers
2k
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 <...
- 34.1k
11
votes
2
answers
833
views
Dr. StrangeNumbers or: How I Learned to Stop Worrying and Love Floating Point Arithmetic
The following is the program.
...
- 403
46
votes
4
answers
10k
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 ...
- 10.1k
30
votes
6
answers
2k
views
How to implement dual numbers in Mathematica?
I wonder how can I implement dual numbers in Mathematica, so that all functions work well with them (as with complex numbers).
Particularly, for each function $f$, $f(\varepsilon)=f^\prime(0)\...
- 3,553