https://github.com/erikhuizinga/findduplicates
A MATLAB function to find linear indices of duplicates in input.
https://github.com/erikhuizinga/findduplicates
Last synced: 3 months ago
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A MATLAB function to find linear indices of duplicates in input.
- Host: GitHub
- URL: https://github.com/erikhuizinga/findduplicates
- Owner: erikhuizinga
- License: gpl-3.0
- Created: 2016-08-30T16:51:43.000Z (almost 9 years ago)
- Default Branch: master
- Last Pushed: 2018-01-19T13:55:46.000Z (over 7 years ago)
- Last Synced: 2025-04-10T06:05:30.913Z (3 months ago)
- Language: Matlab
- Homepage: https://erikhuizinga.github.io/findduplicates/
- Size: 473 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
[](https://mathworks.com/matlabcentral/fileexchange/57532-findduplicates) 
# `findduplicates`, find linear indices of duplicates in input
This function accepts the same input arguments as the [`unique`](http://mathworks.com/help/matlab/ref/unique.html) function, which is the basis for this function.
## Syntax
```MATLAB
[i1, i2] = findduplicates(A)
[i1, i2] = findduplicates(A, setOrder)
[i1, i2] = findduplicates(A, occurence)
[i1, i2] = findduplicates(A, _, 'rows')
[i1, i2] = findduplicates(A, 'rows', _)
[i1, i2, C, ia, ic] = findduplicates(_)
[i1, i2, C, ia, ic] = findduplicates(A, 'legacy')
[i1, i2, C, ia, ic] = findduplicates(A, 'rows', 'legacy')
[i1, i2, C, ia, ic] = findduplicates(A, occurrence, 'legacy')
[i1, i2, C, ia, ic] = findduplicates(A, 'rows', occurrence, 'legacy')
[i1, i2, C, ia, ic] = findduplicates(A, occurrence, 'rows', 'legacy')
```
## Description
`[i1, i2] = findduplicates(A)` finds the linear indices of duplicates
in input `A`. The accepted input arguments are the same as accepted by
the `unique` function. The first output, `i1`, contains the linear indices
of the first duplicate elements into `A` that correspond to the
duplicates indexed by `i2`, the second output. `i1` may contain the same
index multiple times if an element exists more than twice in `A`. If no
duplicates exist, `i1` and `i2` are returned empty.
`[i1, i2] = findduplicates(A, setOrder)` supports the `'sorted'` (default)
or `'stable'` flags of the `unique` function, but have no effect to find
duplicates.
`[i1, i2] = findduplicates(A, occurence)` specifies which duplicate to
consider as the first, `occurence` can be `'first'` (default) or `'last'`.
`[i1, i2] = findduplicates(A, _, 'rows')` and `[i1, i2] = findduplicates(A, 'rows', _)`
treat each row of `A` as a single entity
and returns indices of duplicate rows. You must specify `A` and
optionally can specify `setOrder` or `occurence`. The `'rows'` option does
not support `cell` arrays.
`[i1, i2, C, ia, ic] = findduplicates(_)` also returns `C`, `ia` and `ic`
such that `[C, ia, ic] = unique(_)`. See the documentation for `unique`
for their meaning and use.
The syntaxes with the `'legacy'` option preserve the behaviour this
function would have on R2012b and prior releases. The `'legacy'` option
must be the last input argument. It does not support `categorical`
arrays, `datetime` arrays, `duration` arrays, tables or timetables.
## Examples
### Find the first indices of duplicates and the other duplicates' indices
```MATLAB
A = [9, 2, 9, 5]
[i1, i2] = findduplicates(A)
```
Result
```
A =
9 2 9 5
i1 =
1
i2 =
3
```
This indicates that the first element in `A` has a duplicate at the
third element.
### Find the last indices of duplicate character arrays and the other duplicates' indices
```MATLAB
names = {'Charlie', 'Alice', 'Bob', 'Alice', 'Alice', 'Charlie'};
[i1, i2] = findduplicates(names, 'last')
```
Result
```
i1 =
6
5
5
i2 =
1
2
4
```
This indicates that the character arrays at indices 6 and 5 have
duplicates, 5 having two duplicates. The duplicate for index 6 is
at index 1, the duplicates for index 5 are at indices 2 and 4.
### More examples
Run `findduplicatesdemo` for more examples of `findduplicates` based on
the examples of the `unique` function. See the contents of
findduplicatesdemo.m for details.
## Notes
`NaN` are considered as distinct values by the `unique` function, thus
they are considered non-duplicates by `findduplicates` as well.
## Licence
GNU GPLv3