# Questions tagged [sorting]

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

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### Character edge finding

The following line of code finds the edge of a character: ...
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 ...
2k views

### Ordering problem

Let's look at the following example. Ordering[{0, 20 Sqrt, 40 Sqrt, 20 Sqrt, 20 Sqrt} // N] gives the right answer ...
10k 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 ...
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 ...
3k 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 ...
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 ...
914 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 ...
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 ...
928 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 ...
521 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 ...
382 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: ...
7k views

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

I have some data: ...
602 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: ...
925 views

### Gather list elements by labels

The following list has some elements that are labeled. For example {1, 2} -> 1, {-1, 3} -> 3, etc: ...
538 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 ...
3k 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 ...
3k 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 ...
491 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, ...
2k 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 ...
879 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: ...
868 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: ...
507 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: ...
285 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 ...
6k 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, ...
16k 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: ...
943 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 $a,\ a^\dagger,\ b,\ b^\dagger$ ...
502 views

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

The situation is that I have a List like this: ...
634 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 ...
752 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 ...
1k views

### Lexicographic ordering of lists-of-lists?

I was surprised to discover that Mathematica does not sort lists-of-lists (LLs) lexicographically by default. For example, applying Sort to ...
522 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 ...
351 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 ...
589 views

### Complement[] changes order of elements?

Consider this example: Complement[{a, y, c, d, e}, {a, c}, {d}] (*{e, y}*) However, I was expecting the result to be: ...
349 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)?
810 views

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

I have got a list: ...
857 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 ...
660 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 ...
531 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}}
432 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}
616 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)/...
443 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 ...
219 views

### Problem with Sort - unexpected order with Sqrt [duplicate]

Sort[{13, Sqrt, Sqrt}] (*{13, Sqrt, Sqrt}*) Sort[{13, Sqrt, Sqrt}, #1 < #2 &] (*{Sqrt, Sqrt, 13}*) This seems ...
2k 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}. ...
303 views

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 ...
470 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 ...
680 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 ...
2k 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 ...