The la4j API allows you to calculate the vector norm easily with appropriate vector accumulator. There are three norm accumulators available: Euclidean, Manhattan and Infinity. So, you can use them as

`fold`

arguments in a way like this:Vector a = new BasicVector(new double[]{ 1.0, 2.0, 3.0 }); doble norm0 = a.fold(Vectors.mkEuclideanNormAccumulator()); // Euclidean Norm doble norm1 = a.fold(Vectors.mkManhattanNormAccumulator()); // Manhattan Norm doble normMax = a.fold(Vectors.mkInfinityNormAccumulator()); // Infinity NormWhen norm is available, the distance between two vectors can be calculated as:

Vector a = new BasicVector(new double[]{ 1.0, 2.0, 3.0 }); Vector b = new BasicVector(new double[]{ 4.0, 5.0, 6.0 }); // the distance between vectors 'a' and 'b' in terms of Manhattan space double distance = a.subtract(b).fold(Vectors.mkManhattanNormAccumulator());You also can use norm in order to normalize the vector's components:

Vector a = new BasicVector(new double[]{ 1.0, 2.0, 3.0 }); double norm = a.fold(Vectors.mkEuclideanNormAccumulator()); // normalize 'b' in terms of Eucludean space Vector b = a.divide(norm);

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