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

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21
votes
4answers
1k 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 changes to the other lists so that I ...
19
votes
4answers
672 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 ...
18
votes
11answers
986 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 ...
18
votes
5answers
683 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 ...
17
votes
3answers
336 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: ...
16
votes
2answers
522 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 ...
14
votes
3answers
1k views

Sort per column

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 ...
14
votes
4answers
386 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 ...
14
votes
1answer
200 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: ...
12
votes
6answers
520 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 ...
11
votes
5answers
799 views

Sort date list in format DD/MM/YYYY

I have a list of dates (ranging from 2007 to 2012) in the DD/MM/YYYY format and I need to sort this list. My problem is, when I simply use Sort[] I get: ...
11
votes
2answers
943 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, ...
11
votes
2answers
1k 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 ...
11
votes
1answer
262 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 ...
10
votes
1answer
196 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 ...
9
votes
5answers
2k 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 ...
9
votes
1answer
316 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 like this. ...
9
votes
2answers
431 views

Rearranging a List

I am trying to rearrange/sort a list i.e. {{1,2},{10,140},{43,10},{1,140},{43,2}} into ...
9
votes
2answers
173 views

Why does Sort fail in this simple example?

I'm sure I'll be embarrassed by the answer, but I don't understand why I get the following result: list = {{9, "b"}, {4, "a"}, {7, "k4"}, {6, "k3"}, {5, "w"}} ...
9
votes
1answer
197 views

Ranking Function Allowing for Ties

I have a list that I need to be able to assign ranks to individual elements in, giving it a number related to its position if the list were to be sorted, allowing for ties. For example, ...
8
votes
4answers
315 views

Gather list elements by index

The following list has some elements that are labeled. For example {1, 2} -> 1, {-1, 3} -> 3, etc: ...
8
votes
1answer
173 views

How to tell when a job is too big for the pattern matcher?

Pattern matching is great but it has its limitations. Consider sorting a list of numbers from smallest to largest: ...
8
votes
1answer
247 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 $a,\ a^\dagger,\ b,\ b^\dagger$ ...
7
votes
2answers
217 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}}
7
votes
1answer
214 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 ...
7
votes
3answers
219 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 ...
7
votes
2answers
223 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 ...
6
votes
2answers
286 views

Merging different size, different order table

I'm a beginner in Mathematica, so this may be a simple request. I have generated some columns of names and data. I want to merge them into a single list of names, with a column for each attribute. ...
5
votes
1answer
185 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 ...
5
votes
3answers
379 views

Order list of monomials by degree (Pascal's Triangle)

Suppose I have the following list of monomials: {1,x,x^2,y,y^2,x*y,x^2*y,x*y^2,x^2*y^2} How could I manipulate it to get ...
5
votes
1answer
190 views

Why can't I remove Orderless from Plus?

I am making some random algebra equations, and I want to have the ordering be random too, such that if my random equation generator makes x+1, the output stays ...
4
votes
6answers
236 views

Sorting Matrix elements

I have matrix in as shown, consisting of real numbers and 0. How can I sort it to become out as shown? ...
4
votes
2answers
279 views

Mathematica list element sort

I have a list, say, ...
4
votes
3answers
187 views

Counting number of inversions

Is there an inbuilt method to find the number of inversions in a set of numbers? I found Inversions in Combinatorica but when I ...
4
votes
1answer
154 views

Sorting a list and finding an array of indices that sorts the list

How can I sort a list and also get a list of indices that sort this list? For example: primary list is a a={1,4,6,7,0,2}; sorted list is b ...
4
votes
2answers
135 views

Sorting list with variable

I want to sort (or sortby) the list. List contains uninitialized variable m and I can assume that m is a Natural number that is much larger then any constant. ...
4
votes
1answer
159 views

Are there functions or packages in Mathematica to sort subsets in lex order, colex, revlex, etc.?

I am looking for non-canonical sorts of lists. A function that would give: Sort[X, "order type"] With "order type" being colex, revlex, etc.
4
votes
1answer
341 views

How to implement Kemeny-Young method? (rank aggregation problem)

Prehistory I am trying to make some statistical analysis of some experimental data, arises from measurements made ​​on an ordinal scale. I faced with the problem of rank aggregation: to get from ...
4
votes
2answers
241 views

Sorting a matrix alphanumerically

Somewhat related to Sort matrix by columns and rows without changing them, but more general. I'd like to sort a square matrix (a 3 by 3 in my case, but surely the general solution will treat any), ...
3
votes
2answers
137 views

Import multiple files from folder in order of date added

I have a folder that contains certain files I want to import. In my case those are .png files. As all the files I want to import contain the phrase "accum" in their filenames, I can use ...
3
votes
3answers
138 views

Properly ordering the output of FileNames for a directory consisting of files with consecutive integer names [duplicate]

Say I have a number of files in a directory at some location (C:\dir1\dir2\dir3...), and I pull an array of strings corresponding to the file names with the command: ...
3
votes
1answer
53 views

Order imported files by their alteration date

Probably a very easy question, but I could not find the answer, so it would be very nice if you can help me: Let us say I have 10 files, all with the extension ...
3
votes
2answers
164 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 ...
3
votes
1answer
148 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 ...
3
votes
2answers
100 views

Non-canonical re-ordering of nested lists

I have some data in the form: ...
3
votes
1answer
143 views

Sorting an Array with words in different languages

Array consists of words of different languages. I need to sort elements in reverse alphabetical order and make a list of elements, which consist of english letters. Example of array which consist of ...
2
votes
2answers
223 views

Position function not always retuning 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 ...
2
votes
3answers
244 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
107 views

Confused behavior using Dispatch to sort one list relative to another

I have a need to sort the entries of one list into the same sequence as the entries in a reference list. Because I have rather large lists involving strings, I'm trying to use Dispatch to accomplish ...