Linked Questions

312
votes
12answers
58k 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 ...
35
votes
6answers
2k 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 ...
49
votes
2answers
2k 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 ...
23
votes
6answers
1k views

Mathematica Destructuring

Context I'm writing a function that look something like: ...
13
votes
6answers
834 views

Efficient conditional Mean[] on a large data set

Consider a list, AK6, that has 382 sublists of length varying from 2500 to 3000. Each "subsublist" is as such : ...
27
votes
5answers
2k 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 ...
15
votes
8answers
566 views

UnFlatten an array into a ragged matrix

Trying to unflatten an array that was part of ragged array of sub matrices. As input we have flattened array: ...
11
votes
8answers
460 views

Any built-in function to generate successive sublists from a list?

Given lst = {a, b, c, d} I'd like to generate {{a}, {a, b}, {a, b, c}, {a, b, c, d}} but using built-in functions only, ...
8
votes
7answers
608 views

Populate an upper triangular matrix from a vector of elements

What is the best way to populate an upper triangular (or alternatively: lower triangular or symmetric) matrix from a vector of elements? This example input: ...
17
votes
6answers
773 views

On generalizing Partition[] (with offsets) to sublists of unequal length

The usual Partition[] function is a very handy little thing: ...
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: ...
6
votes
3answers
404 views

Counting the number of a specific type of permutation

In the theory of cumulants of vector-valued random variables, the following types of formulas appear: \begin{equation} \theta^i \theta^{jk} [3] = \theta^i \theta^{jk} + \theta^j \theta^{ik} + \theta^k ...
3
votes
6answers
328 views

How can I construct a distance table?

I have a list of city names (of arbitrary length), f.e. c = {"BAL", "NYC", "LAS", "AUS"}; and the distances between them : ...
6
votes
3answers
644 views

Subsets of a list

Consider the following demand of products for the next four months. data={1,20,3,40}; I could produce the whole demand in the first months, leading to the ...
8
votes
4answers
370 views

Exporting data extensions in fits file

Context In Astronomy the de facto standard for images and data is FITS. I would like to export heterogenous data sets into a single fits file. Attempt I am interested in exporting into a fits file ...

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