Find nearest neighbors by edit distance (2024)

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Find nearest neighbors by edit distance

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Syntax

idx = knnsearch(eds,words)

[idx,d] = knnsearch(eds,words)

[idx,d] = knnsearch(eds,words,Name,Value)

Description

example

idx = knnsearch(eds,words) finds the indices of the nearest neighbors in the edit distance searcher eds to each element in words.

example

[idx,d] = knnsearch(eds,words) also returns the edit distances between the elements of words and the nearest neighbors.

example

[idx,d] = knnsearch(eds,words,Name,Value) specifies additional options using one or more name-value pair arguments.

Examples

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Find Nearest Words

Open Live Script

Create an edit distance searcher.

vocabulary = ["Text" "Analytics" "Toolbox"];eds = editDistanceSearcher(vocabulary,2);

Find the nearest words to "Test" and "Analysis".

words = ["Test" "Analysis"];idx = knnsearch(eds,words)
idx = 2×1 1 2

Get the words from the vocabulary using the returned indices.

nearestWords = 1x2 string "Text" "Analytics"

Find Edit Distances to Nearest Words

Open Live Script

Create an edit distance searcher.

vocabulary = ["MATLAB" "Text" "Analytics" "Toolbox"];eds = editDistanceSearcher(vocabulary,2);

Find the nearest words and their edit distances to "Test" and "Analysis".

words = ["Test" "Analysis"];[idx,d] = knnsearch(eds,words)
idx = 2×1 2 3
d = 2×1 1 2

Get the words from the vocabulary using the returned indices.

nearestWords = eds.Vocabulary(idx)
nearestWords = 1x2 string "Text" "Analytics"

Changing the word "Test" to "Text" requires one edit: a substitution. Changing the word "Analysis" into "Analytics" requires two edits: a substitution and an insertion.

Find Multiple Neighbors

Open Live Script

Create an edit distance searcher.

vocabulary = ["MathWorks" "MATLAB" "Analytics"];eds = editDistanceSearcher(vocabulary,5);

Find the two nearest words and their edit distances to "Math" and "Analysis".

words = ["Math" "Analysis"];idx = knnsearch(eds,words,'K',2)

View the two closest words to "Math".

idxMath = idx(1,:);newWords = eds.Vocabulary(idxMath)
newWords = 1x2 string "MathWorks" "MATLAB"

There is only one word within the maximum edit distance from "Analysis", so the function returns NaN for the other indices. View the nearest words with valid indices.

idxAnalysis = idx(2,:);idxAnalysis(isnan(idxAnalysis)) = [];newWords = eds.Vocabulary(idxAnalysis)
newWords = "Analytics"

Input Arguments

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edsEdit distance searcher
editDistanceSearcher

Edit distance searcher, specified as an editDistanceSearcher object.

wordsInput words
string vector | character vector | cell array of character vectors

Input words, specified as a string vector, character vector, or cell array of character vectors. If you specify words as a character vector, then the function treats the argument as a single word.

Data Types: string | char | cell

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: knnsearch(eds,words,'K',3) finds the nearest three neighbors in eds to the elements of words.

KNumber of nearest neighbors to find
1 (default) | positive integer

Number of nearest neighbors to find for each element in words, specified as a positive integer.

Example: 'K',3

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

IncludeTiesOption to include neighbors whose distance values are equal
false (default) | true

Option to return neighbors whose distance values are equal, specified as true or false.

If 'IncludeTies' is false, then the function returns the K neighbors with the shortest edit distance, where K is the number of neighbors to find. In this case, the function outputs N-by-K matrices, where N is the number of input words. To specify K, use the 'K' name-value pair argument.

If 'IncludeTies' is true, then the function also returns the neighbors whose distances are equal to the Kth smallest distance in the output. In this case, the function outputs cell arrays of size N-by-1, where N is the number of input words. The elements of the cell arrays are vectors with at least K elements. The function sorts the neighbors in each vector in ascending order of distance.

Example: 'IncludeTies',true

Data Types: logical

Output Arguments

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idx — Indices of nearest neighbors in searcher
matrix | cell array of vectors

Indices of nearest neighbors in the searcher, returned as a matrix or a cell array of vectors.

If 'IncludeTies' is false, then the function returns the K neighbors with the shortest edit distance, where K is the number of neighbors to find. In this case, the function outputs N-by-K matrices, where N is the number of input words. To specify K, use the 'K' name-value pair argument.

If 'IncludeTies' is true, then the function also returns the neighbors whose distances are equal to the Kth smallest distance in the output. In this case, the function outputs cell arrays of size N-by-1, where N is the number of input words. The elements of the cell arrays are vectors with at least K elements. The function sorts the neighbors in each vector in ascending order of distance.

Data Types: double | cell

d — Edit distances to neighbors
matrix | cell array of vectors

Edit distances to neighbors, returned as a matrix or a cell array of vectors.

If 'IncludeTies' is false, then the function returns the K neighbors with the shortest edit distance, where K is the number of neighbors to find. In this case, the function outputs N-by-K matrices, where N is the number of input words. To specify K, use the 'K' name-value pair argument.

If 'IncludeTies' is true, then the function also returns the neighbors whose distances are equal to the Kth smallest distance in the output. In this case, the function outputs cell arrays of size N-by-1, where N is the number of input words. The elements of the cell arrays are vectors with at least K elements. The function sorts the neighbors in each vector in ascending order of distance.

Data Types: double | cell

Version History

Introduced in R2019a

See Also

correctSpelling | editDistance | editDistanceSearcher | rangesearch | splitGraphemes | tokenizedDocument

Topics

  • Correct Spelling in Documents
  • Create Extension Dictionary for Spelling Correction
  • Create Custom Spelling Correction Function Using Edit Distance Searchers
  • Prepare Text Data for Analysis
  • Create Simple Text Model for Classification
  • Analyze Text Data Using Topic Models

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Find nearest neighbors by edit distance (2024)

FAQs

How do you calculate the nearest neighbor distance? ›

The average nearest neighbor ratio is calculated as the observed average distance divided by the expected average distance (with expected average distance being based on a hypothetical random distribution with the same number of features covering the same total area).

What is the edited nearest neighbor rule? ›

Edited Nearest Neighbor is an under-sampling method that edits the majority set by removing some of the majority samples from the original majority set.

How to calculate KNN distance? ›

The most intuitive and widely used distance metric for KNN is the Euclidean distance, which is the straight-line distance between two points in a vector space. It is calculated by taking the square root of the sum of the squared differences between the corresponding coordinates of the two points.

What is the formula for the distance rule? ›

Distance between two points is the length of the line segment that connects the two points in a plane. The formula to find the distance between the two points is usually given by d=√((x2 – x1)² + (y2 – y1)²).

What is nearest neighbor distance matching? ›

NNDM is a variant of leave-one-out cross-validation which assigns each observation to a single assessment fold, and then attempts to remove data from each analysis fold until the nearest neighbor distance distribution between assessment and analysis folds matches the nearest neighbor distance distribution between ...

What is nearest neighbor distance algorithm? ›

A nearest neighbor algorithm plots all vectors in a multi-dimensional space and uses each of the points to find a neighboring point that is nearest. Different types of nearest neighbor algorithms consider a neighboring point differently (more on that later).

Which is the nearest neighbor method? ›

Nearest-Neighbor Classifiers

This method finds the closest training set object in the N-dimensional feature space that is closest to the object being classified.

What is the approximate nearest neighbor method? ›

Broadly speaking, approximate k-nearest-neighbor search algorithms — which find the k neighbors nearest the query vector — fall into three categories: quantization methods, space-partitioning methods, and graph-based methods. On several benchmark datasets, graph-based methods have yielded the best performance so far.

How to find nearest neighbors in KNN algorithm? ›

Step-1: Select the number K of the neighbors. Step-2: Calculate the Euclidean distance of K number of neighbors. Step-3: Take the K nearest neighbors as per the calculated Euclidean distance.

What is the formula for nearest neighbor analysis? ›

A is calculated by (Xmax - Xmin) * (Ymax - Ymin). Refined nearest neighbor analysis involves comparing the complete distribution function of the observed nearest neighbor distances, , with the distribution function of the expected nearest neighbor distances for CSR, .

How to calculate nearest Neighbour distance in FCC? ›

The nearest distance is the distance between centre of these atoms. This distance is the half of the length of face diagonal which is equal to: 12×√2 a⇒Nearest distance: a√2. Q.

What is the nearest neighbor estimation method? ›

Finding the nearest neighbor is the process of plotting all the vectors in all their dimensions and then comparing a context collection of vectors to them. Using a simple coordinate system you can mathematically measure how far one point is from another (known as their distance).

References

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