matchpt: Nearest neighbor search.
In Biobase: Biobase: Base functions for Bioconductor

Description Usage Arguments Details Value Author(s) Examples

Find the nearest neighbors of a set of query points in the same or another set of points in an n-dimensional real vector space, using the Euclidean distance.

1	matchpt(x, y)

`x`	A matrix (or vector) of coordinates. Each row represents a point in an `ncol(x)`-dimensional real vector space.
`y`	Optional, matrix (or vector) with the same number of columns as `x`.

If y is provided, the function searches for each point in x its nearest neighbor in y. If y is missing, it searches for each point in x its nearest neighbor in x, excluding that point itself. In the case of ties, only the neighbor with the smaller index is given.

The implementation is simple and of complexity nrow(x) times nrow(y). For larger problems, please consider one of the many more efficient nearest neighbor search algorithms.

A data.frame with two columns and nrow(x) rows. The first column is the index of the nearest neighbor, the second column the distance to the nearest neighbor. If y was given, the index is a row number in y, otherwise, in x. The row names of the result are those of x.

Oleg Sklyar osklyar@ebi.ac.uk

    a <- matrix(c(2,2,3,5,1,8,-1,4,5,6), ncol=2L, nrow=5L)
    rownames(a) = LETTERS[seq_len(nrow(a))]
    matchpt(a)
    b <- c(1,2,4,5,6)
    d <- c(5.3, 3.2, 8.9, 1.3, 5.6, -6, 4.45, 3.32)
    matchpt(b, d)
    matchpt(d, b)

Loading required package: BiocGenerics
Loading required package: parallel

Attaching package: 'BiocGenerics'

The following objects are masked from 'package:parallel':

    clusterApply, clusterApplyLB, clusterCall, clusterEvalQ,
    clusterExport, clusterMap, parApply, parCapply, parLapply,
    parLapplyLB, parRapply, parSapply, parSapplyLB

The following objects are masked from 'package:stats':

    IQR, mad, sd, var, xtabs

The following objects are masked from 'package:base':

    Filter, Find, Map, Position, Reduce, anyDuplicated, append,
    as.data.frame, basename, cbind, colMeans, colSums, colnames,
    dirname, do.call, duplicated, eval, evalq, get, grep, grepl,
    intersect, is.unsorted, lapply, lengths, mapply, match, mget,
    order, paste, pmax, pmax.int, pmin, pmin.int, rank, rbind,
    rowMeans, rowSums, rownames, sapply, setdiff, sort, table, tapply,
    union, unique, unsplit, which, which.max, which.min

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  index distance
A     5 2.236068
B     3 5.099020
C     4 2.236068
D     3 2.236068
E     1 2.236068
  index distance
1     4     0.30
2     4     0.70
3     7     0.45
4     1     0.30
5     5     0.40
  index distance
1     4     0.30
2     3     0.80
3     5     2.90
4     1     0.30
5     5     0.40
6     1     7.00
7     3     0.45
8     3     0.68