# Tagged Questions

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

702 views

### How do I sort complex numbers?

Okay, so I posted something about sorting, and it was linked as a duplicate to This post However, I am having problems trying to sort a list that contains both real and complex numbers. I put them ...
120 views

### Challenging matrix sorting request?

I have an application in mind, and I need to do the following analysis, but am having a high degree of difficulty conceptualizing it in terms of syntax. I understand what I want, but cannot seem to ...
376 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 ...
128 views

### Arrangement Order and Multiple Columns Sorting Order of Associations with Missing Keys

I have the following well-formed JSON string ...
59 views

### How to canonically reorganize a list using only a limited set of manipulations?

I want to canonically reorganize (like Sort) a sequence of four objects seq[a,b,c,d], but the only manipulations allowed are <...
349 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 ...
100 views

### SameQ for unsorted lists

I have to compare two or more lists and check if they are the same, but their elements can be in different position. For instance ...
81 views

### Descending order of Permutations using Select[Tuples[{5, 4, 3, 2, 1}, {3}], OrderedQ]

I was wondering if there is a possible way to still use OrderedQ and get a descending order of permutations: This is Ascending order: ...
33 views

### I have trouble in sorting a matrix in wolfram mathematica [duplicate]

I have an array of five elements, I have to make permutations of 3 elements. I have my code: A = {1, 2, 3, 4, 5}; n = Permutations[A, {3}]; Now I have to sort ...
1k views

### Sort matrix by columns and rows without changing them

I would like to sort a matrix in descending order first by the total of each column, then by the total of each row, but without changing their content. For example, if I had: ...
34 views

### Sorting orthogonal null space vectors

My program generates orthogonal null space vectors such as this: ...
488 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 ...
217 views

### Are there any good mass row/column swapping functions for matrices?

I have the following matrix Keeping the 20 row and 20 column fixed (so the 21st rows and columns because I started at 0)...how do I push each row and column back one spot? I need to push the 0th row ...
112 views

### Find list item before first negative value [closed]

If I have a list like this: ...
233 views

### How to sort the list of all possible 3-tuples of elements from list constrained by a condition?

I want to know if there's a way to impose desired condition on Tuple command output. I have generated a list of 3-tuple of elements from {1,2,3,4,5,6,7,8,9,10} ...
93 views

### Sorting non-numerical lists [duplicate]

The Sort function will by default sort from lowest to highest. In[1]:= Sort[{3, 1, 4}] Out[1]= {1, 3, 4} However, if the list ...
194 views

### Collision detection algorithm (discrete) with sweep and prune algorithm for periodic boundary conditions

EDIT: Question Updated with solution approach, but solution much slower than original implementation. Any ideas to speed up implementation? In the discussion on collision detection (see here) I asked ...
371 views

### Is there an inequality operator (Less, Greater) for lists of elements (as opposed to elements)?

Like multi-column sorting. For example, {1,3,5} > {1,2,5} would return True, while ...
337 views

### Finding minimum of a list of pairs

Sometimes I need to find the Min of a list, whose elements are lists (say of two elements, a pair). Given that Min does not have the option to indicate a sorting function like Sort, I elaborated the ...
64 views

### Error with using SortBy in a Map [closed]

I have a data set in the following format: SomeData = {{a, 1, 2}, {b, 2, 3}, {c, 3, 4}, {b, 1, 9}, {c, 1, 10}, {a, 2, 3}, {a, 3, 8}, {b, 3, 4}, {c, 2, 9}}; The ...
45 views

### How do I reassign canonical ordering of special expressions?

1. Default behavior of Sort Note: this peculiarity is described in a comment to a related question at StackOverflow but I think it's worth restating here at mma.sx. It is estabilished in ...
25 views

### Sort giving unexpted output! [duplicate]

I want to perform sorting on a list of strings, If i take for example the list s s={"test9","test8","test10"}; If i perform the Sort function i will get: ...
120 views

### Importing, sorting and exporting lists

I have several TSV lists (.txt) of something like 2000*2000 numerics (e.g. 1.8645) to import ...
102 views

### While subpartitioning the elements in list using GatherBy, can I corresponding subpartition the elements of an unrelated list?

If we have a list like the following: list1 = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}; And we use GatherBy to subpartition is according to a test function <...
153 views

### ordered tree data structure

I have a map $f:X\to \mathbb{N}$ and I wish to find $x,x'\in X$ such that $f(x)=f(x')$. Since such elements are rare, I will have to check very many elements and perform many comparisons, so I suspect ...
1k 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 ...
43 views

### Breaking term order ties [duplicate]

I am interested in creating a table with positive Gaussian integers listed in order based on their norms, with ties broken by lex order. So far I have ...
601 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: ...
283 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). ...
248 views

### Multicolumn sorting with ordering functions and precedence

I am aware that the question of "how do I sort on a column" has been asked in various forms, most notably this one. While some powerful solutions have been presented, as far as I can find no one ...
2k 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, ...
122 views

### How to get the ranked order

data = {33, 6, 10}; Ordering[data] (* {2, 3, 1} *) What I really want is, 3 for 33, as it is the 3rd, if sorted; 1 for 6, as it is the 1st, if sorted; and 2 for ...
114 views

### Comparing two lists lexically

I have two lists of integers a and b of equal length, and I would like to define a>b as ...
365 views

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

The situation is that I have a List like this: ...
481 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: ...
75 views

### Disabling Mathematica's automatic sort of output

I used Mathematica to greatly simplify an algebraic expression. I now want to copy it into some notes, but it by defaults things in a very non-intuitive manner. I have a sorting function that will ...
307 views

### SortBy misbehaving?

It maybe a stupid thing in the end but I'm stuck a couple of hours now. I have a list of 2 points on the plane and I want to get the one with the biggest second coordinate. I thought I knew how ...
345 views

### Sorting Lists of lists of arbitrary length

I'm trying to sort a list of lists. The sublists are defined in length, but the length of the list containing it varies. A simplified set might be: ...
762 views

### Collision detection algorithm (discrete) with sweep and prune algorithm

For a more complex collision detection approach, I need an efficient (aka fast) algorithm to prune the elements by using boundary boxes. A classical algorithm is the so called sweep and prune (SAP) ...
175 views

### Sorting out atom types in an XYZ file

I am trying to rewrite the output of "VertexCoordinates" such that instead of a hybrid list of atoms and coordinates that result from using the following input program, I want all coordinates of the ...
418 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 ...
931 views

### Ordering the Boundary points of a Polygon

I feel like this should be simple, but I keep running into walls. Say someone gives you the coordinates of the vertices of a pentagon and the center point of the hexagon. Is there any way to get an "...
96 views

### Place symbols from small to big

I am wondering how to compare the different values of ω I derived in this code, and place them in order as follows. (use Print ...
495 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 ...
344 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 ...
335 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 ...
330 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 ...
180 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 .dat...