Linked Questions
33 questions linked to/from How to efficiently find positions of duplicates?
6
votes
4
answers
514
views
1
vote
4
answers
316
views
Using Select in Subsets [duplicate]
I have a list:
list = {{7, 6, 14, 14, 4}, {4, 9, 8, 11, 14}, {20, 12, 12, 11, 3}, {7,
4, 11, 7, 20}, {2, 13, 17, 11, 19}}
I did a test to identify where ...
user45150
5
votes
2
answers
149
views
Position of first element in list which is repeated [duplicate]
I have the list
t1 = {{-1, 0}, {-2, 0}, {-3, 0}, {0, 0}, {-2, 0}, {1, 1}}
How do I find the position where an element repeats? In this case it would be element <...
- 2,020
584
votes
19
answers
148k
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 ...
76
votes
8
answers
6k
views
Partitioning with varying partition size
How can I partition a list into partitions whose sizes vary?
The length of the $k$'th partition is a function $f(k)$.
For example: if $l = \{1, 2, 3, 4, 5, 6\}$ and $f(k) = k$. Then
the partitioning ...
- 7,337
22
votes
13
answers
4k
views
How to get list of duplicates when using DeleteDuplicates?
This might be easy, but can't find a way to use DeleteDuplicates to get also list of the actual duplicates.
Example:
...
- 108k
12
votes
4
answers
7k
views
Delete duplicate elements from a list
If a list contains duplicate elements, for example
list = {a, 1, 5, 3, 5, x^2, x^2},
how can the duplicate elements be removed? The result would be
...
- 7,337
23
votes
6
answers
4k
views
Looking for a way to insert multiple elements into multiple positions simultaneously in a list
I would like to take the following data:
insertValues = {r, x};
insertPositions = {{1}, {5}};
originalList = {a, b, c, d, e, f, g};
and generate output that ...
- 2,024
12
votes
11
answers
526
views
Positions of elements in the initial flattened list in a split list
Say, we have a list:
m1 = {2, 2, 7, 0, 7, 7, 2, 2, 2}
It can be split easily:
...
- 4,735
23
votes
7
answers
2k
views
How do I obtain an intersection of two or more list of lists conditioned on the first element of each sub-list?
Given two lists like
list1 = {{1, 1}, {2, 4}, {3, 9}, {4, 16}};
list2 = {{2, 6}, {3, 9}, {4, 12}, {5, 15}};
I would like to produce an output like
...
- 908
47
votes
3
answers
1k
views
Why is the new PositionIndex horribly slow?
This issue has largely been mitigated in 10.0.1. New timings for the final test below are:
...
- 264k
26
votes
5
answers
961
views
Partitioning a list when the cumulative sum exceeds 1
I have a long list of say 1 million Uniform(0,1) random numbers, such as:
dat = {0.71, 0.685, 0.16, 0.82, 0.73, 0.44, 0.89, 0.02, 0.47, 0.65}
I want to ...
- 8,441
17
votes
6
answers
592
views
Pick elements from list "separately"
I have the following list I want to pick elements from:
mylist = {1, 5, 7, 3, 4, 7, 2, 9, 9, 1, 10, 12, 2, 64, 34, 64}
I have another list with 0's and 1's which ...
- 2,703
19
votes
5
answers
1k
views
Easiest/most efficient way to delete duplicates from one list at the positions of another?
This question is somewhat related to How to efficiently find positions of duplicates? , although I'm interested in something a little bit simpler since I'm not really interested in a list of all the ...
- 191
13
votes
5
answers
3k
views
Match opening and closing parentheses?
Suppose I have a List of the form:
lst={"(", "(", "(", ")", "(", ")", ")", ")"}
By running ...
- 10.7k