Linked Questions

10
votes
5answers
4k views

How to subtract one list from another, treating each elements as distinct, assuming the smaller list is a subset of the larger list? [duplicate]

Suppose that I have two lists of different sizes, the smaller of which is a subset of the larger, e.g. a = {"A", "A", "A", "B", "B", "C"} b = {"A", "B"} How can ...
5
votes
4answers
228 views

Efficient way to compute a complement while respecting multiplicities [duplicate]

Suppose I have list2 which is a subset of list1. I want to get a res by deleting an element ...
2
votes
3answers
330 views

Deleting one of each chosen elements in a list containing duplicates [duplicate]

I want to delete one of each (and not all) selected element in a list containing duplicates. For example i have the list: $\{1,1,1,2,2,3\}$ and i want to delete $\{1,3\}$ so the leftover should be $\{...
2
votes
3answers
412 views

How to do subtraction with sets in which the elements have multiplicity indicators? [duplicate]

I want to do subtraction with sets l1 and l2, which contain multiplicity indicators. For example, ...
1
vote
1answer
133 views

What is the fastest way to delete multiple entries from a list? [duplicate]

Mathematica allows Deleting multiple objects from a list given their position. However, if I don't know their positions (finding their positions in the list is too costly if the list is long), how can ...
1
vote
0answers
85 views

Removing every member of a list from another list [duplicate]

I have a list of lists A={{1,2},{3,6},{7,8},{5,0}}, and another list of lists B={{1,2},{5,0}}. If any list in B is also in A, I want to remove them from A. E.g.,Taking {1,2} and {5,0} out of A to get ...
526
votes
19answers
130k views

Where can I find examples of good Mathematica programming practice?

I consider myself a pretty good Mathematica programmer, but I'm always looking out for ways to either improve my way of doing things in Mathematica, or to see if there's something nifty that I haven't ...
36
votes
6answers
9k views

How to Delete Elements from List1 appearing in List2?

I'm new to functional programming of Mathematica and trying to remove one list of assorted elements from another. However I only find functions working with the Index rather than the values itself: ...
18
votes
8answers
1k views

How do I delete all items that occur more than once?

DeleteDuplicates works fine but leaves a single copy of the duplicated item. I need to remove all items that occur more than once i.e. {{1,2},{1,2},{3,4}} -> ...
13
votes
8answers
2k views

Given an ordered set S, find the points in S corresponding to another list

Given a sorted list of numbers $S$, I want to create a function that accepts a list of numbers $L$ and for each number $l \in L$ it returns the index of the largest number $s \in S$ such that $s<l$....
13
votes
5answers
1k views

Filtering elements from a list that appear only once

I want to be able to select elements from a list that only appear once. I originally had this: Select[Table[Count[list, i], {i, list}], # == 1] But the issue is ...
10
votes
6answers
687 views

Efficiently finding the positions of a large list of targets in another, even larger list

I have a big list. It contains nearly 60,000 sub-lists. It's structured like bigList = {{x1,y1,z1},{x2,y2,z2},{x3,y3,z3},.....,{x60000,y60000,z60000}}; I have ...
10
votes
4answers
588 views

Complement of multisets

Given lists $a$ and $b$, which represent multisets, how can I compute the complement $a\setminus b$? I'd like to construct a function xunion that returns the ...
11
votes
5answers
2k views

Find all the possible ways of partitioning a list into a set of pairs of element

I have a list {x1,...,xN} where N is even, and I need to find all the possible ways to split it into pairs of elements, e.g. the ...
15
votes
2answers
1k views

Vlookup function as Excel in Mathematica

How can we create a Vlookup function, similar to what we have in Excel? So if we have a table a and another b, we could add ...

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