`L2_distance.Rd`

Quickly calculates and returns the Euclidean distances between m vectors in one set and n vectors in another. Each set of vectors is given as the columns of a matrix.

L2_distance(a, b, df = 0)

a | A d by m numeric matrix giving the first set of m vectors of dimension d
as the columns of |
---|---|

b | A d by n numeric matrix giving the second set of n vectors of dimension d
as the columns of |

df | Indicator whether to force the diagonals of the returned matrix to
be zero ( |

An m by n matrix containing the Euclidean distances between the column
vectors of the matrix `a`

and the column vectors of the matrix `b`

.

This fully vectorized (VERY FAST!) function computes the Euclidean distance between two vectors by:

||A-B|| = sqrt ( ||A||^2 + ||B||^2 - 2*A.B )

Originally written as L2_distance.m for Matlab by Roland Bunschoten of the University of Amsterdam, Netherlands.

A <- matrix(rnorm(400), nrow = 10) B <- matrix(rnorm(800), nrow = 10) L2_distance(A[,1, drop = FALSE], B[,1, drop = FALSE])#> [,1] #> [1,] 6.139374d_AB <- L2_distance(A,B) d_BB <- L2_distance(B,B, df = 1) # force diagonal to be zero