Questions tagged [sorting]

Questions on the sorting/ordering functions of Mathematica (Sort, SortBy, Ordering, etc.).

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49
votes
7answers
3k views

Character edge finding

The following line of code finds the edge of a character: ...
17
votes
7answers
5k views

How to find rows that have maximum value?

Suppose if I have following list { {10,b,30}, {100,a,40}, {1000,b,10}, {1000,b,70}, {100,b,20}, {10,b,70} } How to find rows that have max value in ...
23
votes
2answers
1k views

Ordering problem

Let's look at the following example. Ordering[{0, 20 Sqrt[5], 40 Sqrt[5], 20 Sqrt[5], 20 Sqrt[10]} // N] gives the right answer ...
37
votes
4answers
9k views

Sort lists according to the order of another

I have three parallel lists (i.e. the elements in position i of each list are related). I want to sort the first list using the function Sort and make the same ...
31
votes
5answers
3k views

How do I reassign canonical ordering of symbols?

I have a big polynomial that evaluates to: $$A^2 e^2 \phi ^- \phi ^++A e \phi ^- \phi ^+ c_{2 w} g_Z+\frac{1}{2} A e g h W^- \phi ^+ +\ll13\gg,$$ which is supposed to represent some terms in the ...
7
votes
3answers
2k views

How to plot several functions without jumping? (multiple eigenvalues of a system as functions of 2 parameters)

I've been working on this research problem for months with some success by no global/proper solution to the problem. So I have square, Hermitian matrices of various sizes ($8,20,38$ dimensions) with ...
7
votes
2answers
784 views

Position function not always returning an answer even with no apparent problems

I'm having some problems with Position. Sometimes it will give an empty list instead of the actual position of the element I am looking for when that element is ...
25
votes
4answers
2k views

Sort strings by natural ordering

Is there an easy way to sort strings according to their natural ordering? For example a list of file names ...
30
votes
3answers
1k views

Is there a “precedence table” for the canonical Sort ordering?

This answer in which I wrote about the Operator Precedence Table was unexpectedly popular. That got me thinking about similar things, and I am wondering: Does an "ordering table" exist for the ...
13
votes
6answers
886 views

Sort+Union on a list

Probably this is too trivial question for this forum but for some reason I am not getting it on my Mathematica 7 so far. I have a list ...
14
votes
3answers
468 views

Retaining and reusing a one-to-one mapping from a sort

Imagine I sort the elements of an array $Q$ by some means. Perhaps I sort strictly by the elements in the first column, perhaps I use SortBy[...] to sequentially sort by the elements in successive ...
17
votes
1answer
360 views

Ordering function with recognition of duplicates

Fairly often I have a need to get the Ordering of an expression but with recognition of duplicates. For example: ...
28
votes
5answers
7k views

Sort data after specific ordering (ascending/descending) in multiple columns

I have some data: data={{"a", 1, 1}, {"a", 1, 2}, {"a", 1, 3}, {"c", 2, 1}, {"b", 2, 2}, {"b", 2, 3}, {"c", 3, 1}, {"a", 3, 2}, {"a", 3, 3}} When I ...
11
votes
4answers
863 views

Gather list elements by labels

The following list has some elements that are labeled. For example {1, 2} -> 1, {-1, 3} -> 3, etc: ...
15
votes
4answers
539 views

FindCurvePath for lines (rather than points)

I have need of a function to find a good ordering for a series of lines, as FindCurvePath does for points. Sample data: ...
10
votes
2answers
487 views

Complement on pre-sorted lists

Is there any way to instruct Complement to skip the sorting part? If the answer is no (likely), the next question would be: how can I remove from a sorted list ...
15
votes
2answers
2k views

Simple algorithm to find cycles in edge list

I have the edge list of an undirected graph which consists of disjoint "cycles" only. Example: {{1, 2}, {2, 3}, {3, 4}, {4, 1}, {5, 6}, {6, 7}, {7, 5}} Each ...
23
votes
11answers
2k views

Generating an ordered list of pairs of elements from ordered lists

I have a pair of ordered lists. I want to generate a new ordered list (using the same ordering) of length n by applying a binary operator to pairs of elements, one from each list, along with the index ...
13
votes
4answers
1k views

Difference between Sort and SortBy

I was playing with Sort. All examples I have come across so far, i.e Sort[{1, -1, 3, -3, 2, 5}, Abs[#1]<Abs[#2]&] can expressed in a shorter fashion ...
13
votes
1answer
794 views

How can I collect data for visualization of quick sort?

I know how to implement quick sort in Mathematica. But I don't know how to get the temp data for visualization, because I used recursion. I want the effect similar to this: ...
6
votes
4answers
787 views

Sorting a list of variables by the numerical value they represent

What would be the simplest method of sorting a list of variables according to the value they represent: Let: ...
7
votes
1answer
277 views

How to get all possible orderings (equal ranks allowed) for given set of $N$ objects?

Hope there is a solution besides the tedious generation of nested loops. (Trying to avoid reinventing the wheel.) Here is an example with $N = 3$ objects. There are $13$ needed orderings (first ...
25
votes
2answers
5k views

Sorting a list with secondary criterion

Is there an easy way to sort a list on multiple levels of criteria? By this I mean, first the list should be sorted according by criteria A (the same as using the usual sort function, ...
30
votes
4answers
11k views

How to sort colors properly?

I can't seem to be able to sort colors by their hue and perceptual brightness correctly. Here's my current solution, but it's not right; there are all these dark bands: ...
11
votes
1answer
789 views

Sorting function for non commuting bosons

I am trying to write a sorting function which will sort expressions involving products of bosonic objects which do not commute. For example, I can have objects like $a,\ a^\dagger,\ b,\ b^\dagger$ ...
6
votes
6answers
459 views

Sort a list of coordinates by frequency from first component of each coordinate

The situation is that I have a List like this: ...
5
votes
8answers
589 views

How to sort my list?

For example I have two lists of such structure L1 = {{"Australia",a1}, {"USA",a2}, {"Norway",a3},...} L2 = {{"Russia",b1}, {"Norway",b2}, {"Japan",b3},...} I ...
15
votes
4answers
508 views

How can we implement “Sleep Sort”?

Inspired by Implement Sleep Sort: Sleep Sort is an integer sorting algorithm I found on the Internet. It opens an output stream, and for each input numbers in parallel, delay for the number seconds ...
12
votes
1answer
414 views

ls Ordering[Ordering[list]] optimal?

Given a list list with unique elements, the task is to replace each element by its position in Sort[list]. For example, ...
22
votes
5answers
485 views

Unexpected result {“.a”, “co”, “.m”} from Sort[{“.m”, “.a”, “co”}]

I came across the following situation: Evaluating Sort[{".m", ".a", "co"}] Results in {".a", "co", ".m"} I wondering: ...
10
votes
1answer
323 views

How to pass composite function list to SortBy?

In order to sort alphanumeric-as-string data of the form {"T3", "T14", "T1", "E2"}, so that "T14" comes after ...
4
votes
4answers
509 views

How to pick out the element in a list of lists which satisfies a particular condition?

I have got a list: ...
4
votes
2answers
276 views

Sort by returning positions [duplicate]

How can I computationally efficiently sort a list so as to return the positions and not the actual values at those positions (which SortBy does)?
15
votes
6answers
808 views

Better way to sort course grades

I use the following code to create a histogram of grades. Grades are provided as a List of strings such as "A-", "D+", "E" (don't ask), etc. The +/- substitution hack is necessary to sort the grades ...
10
votes
2answers
587 views

Unexpected behavior when using SortBy as a dataset filter

I am still experimenting with datasets. Recently I tried to query the Titanic example to get info on the oldest passengers. Here is what I tried ...
10
votes
2answers
417 views

How to generate Intervals from a given list?

If I have a list list={3,7,4,5,1} how to get the List of Intervals /Ranges result = {{1,3},{3,4},{4,5},{5,7}}
5
votes
1answer
517 views

Plotting eigenvalues smoothly

I am trying to plot how the eigenvalues of a matrix change by changing a given a parameter t. Of course the ordering of the eigenvalues does not matter mathematically but it does when I want to make ...
3
votes
2answers
242 views

Output all steps of Sort [duplicate]

Is there a way you output each partial result of the Sort function? i.e. Sort[{2,3,1}] {2,1,3} {1,2,3}
2
votes
3answers
434 views

Re-arranging / selecting of a data table very slow in For loop [duplicate]

My task is quite simple; I have a table of data like M = {{1,2}, {1,3}, {3,4}, {5,1}, {6,9}, {6,8}, {6,1}}; so the table is sorted with respect to the first ...
2
votes
1answer
380 views

How can I sort the polynomial by the degree of $x$

f1 = a x^2 + b x + c + x^3 (* a x^2+b x+c+x^3 *) f1 /. x -> (x - a/3) // Expand (* (2 a^3)/...
0
votes
1answer
197 views

Problem with Sort - unexpected order with Sqrt [duplicate]

Sort[{13, Sqrt[157], Sqrt[163]}] (*{13, Sqrt[157], Sqrt[157]}*) Sort[{13, Sqrt[157], Sqrt[157]}, #1 < #2 &] (*{Sqrt[157], Sqrt[157], 13}*) This seems ...
10
votes
3answers
459 views

Wolfram Language symbols by their Ranks

I'd like to get the top 50, the bottom 50 and an ordered list of all Wolfram Language symbols based on their "Ranks". With ...
14
votes
1answer
279 views

Dataset is 20X slow when adding column heads

I'm trying to use Dataset to explore some large data. I notice that the performance decrease more than 20X by adding heads to the columns. Here is an example: We ...
6
votes
2answers
604 views

Sorting a large file

I have some huge logs, which are text files, containing up to a million rows each, and I need them sorted. Because trying to import one obviously makes Mathematica run out of memory, we must rule out ...
14
votes
6answers
948 views

Rearrange the list in a specific way

Suppose I have a list like {"e", "c", "a", "d", "b"} and list of rules {1 -> 5, 2 -> 3, 3 -> 1, 4 -> 4, 5 -> 2}. ...
12
votes
2answers
1k views

Efficiently searching a list for the position of the closest number to a specified number

Searching by closest and position I wasn't able to find an answer—but found Nearest by guessing. Nearest, however, returns ...
10
votes
1answer
447 views

Max element of a list with a custom ordering function

I need a function to find max element of a list according to some custom ordering function, assuming that the function implements a total order (elements being compared might not even be numbers). ...
5
votes
3answers
2k views

Non Commutative sorting in Mathematica

I have been trying to do some oscillator algebra in Mathematica and having troubles with sorting and simplifying expressions. I am using the NCAlgebra package which helps to improve the properties of <...
3
votes
1answer
578 views

Windows Explorer Natural Order

Currently there are a list of notebooks in Windows that I am processing in a folder. Ideally I would like the notebooks to be concated in the same order as how they display in Windows Explorer. I ...
2
votes
2answers
512 views

How to sort Table/Matrix including legend(Labellings)

I want to sort table including its legend for graph I have table similar to M1 M2 M3 1 5 2 3 1 4 4 2 -10 5 7 11 6 -2 1 ...