Questions on the sorting/ordering functions of Mathematica (Sort, SortBy, Ordering, etc.).
12
votes
2answers
772 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 ...
7
votes
5answers
757 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 ...
18
votes
4answers
554 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 ...
18
votes
11answers
645 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 ...
15
votes
2answers
359 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
...
13
votes
3answers
687 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 ...
7
votes
3answers
163 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 ...
9
votes
1answer
133 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 ...
2
votes
2answers
139 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 ...
