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based on an earlier version of the Wolfram Language.
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# Using Nearest

Nearest is used to find elements in a list that are closest to a given data point.
 Nearest[{elem1,elem2,...},x] give the list of elemi to which x is nearest Nearest[{elem1->v1,elem2->v2,...},x] give the vi corresponding to the elemi to which x is nearest Nearest[{elem1,elem2,...}->{v1,v2,...},x] give the same result Nearest[{elem1,elem2,...}->Automatic,x] take the vi to be the integers 1, 2, 3, ... Nearest[data,x,n] give the n nearest elements to x Nearest[data,x,{n,r}] give up to the n nearest elements to x within a radius r Nearest[data] generate a NearestFunction[...] which can be applied repeatedly to different x

Nearest function.

Nearest works with numeric lists, tensors, or a list of strings.
This finds the elements nearest to 4.5.
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This finds 3 elements nearest to 4.5.
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This finds all elements nearest to 4.5 within a radius of 2.
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This finds the points nearest to {1, 2} in 2D.
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This finds the nearest string to "cat".
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The rule-based data syntax lets you use nearest elements to return their labels.
Here two-dimensional points are labeled.
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This labels the elements using successive integers.
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If Nearest is to be applied repeatedly to the same numerical data, you can get significant performance gains by first generating a NearestFunction.
This generates a set of 10,000 points in 2D and a NearestFunction.
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This finds points in the set that are closest to the 10 target points.
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It takes much longer if NearestFunction is not used.
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 option name default value DistanceFunction Automatic the distance metric to use

Options for Nearest.

For numerical data, by default Nearest uses the EuclideanDistance. For strings, EditDistance is used.