# knn

0th

Percentile

##### Spatial K nearest neighbor

Find K nearest neighbors for two spatial objects

Finds nearest neighbor in x based on y and returns rownames, index and distance, If ids is NULL, rownames of x are returned. If coordinate matrix provided, columns need to be ordered [X,Y]. If a radius for d is specified than a maximum search radius is imposed. If no neighbor is found, a neighbor is not returned

You can specify weights to act as covariates for x and y. The vectors or matrices must match row dimensions with x and y as well as columns matching between weights. In other words, the covariates must match and be numeric.

##### Usage
knn(
y,
x,
k = 1,
d = NULL,
ids = NULL,
weights.y = NULL,
weights.x = NULL,
indexes = FALSE
)
##### Arguments
y

Spatial points or polygons object or coordinates matrix

x

Spatial points or polygons object or coordinates matrix

k

Number of neighbors

d

Optional search radius

ids

Optional column of ID's in x

weights.y

A vector or matrix representing covariates of y

weights.x

A vector or matrix representing covariates of x

indexes

(FALSE/TRUE) Return row indexes of x neighbors

##### Value

A data.frame with row indexes (optional), rownames, ids (optional) and distance of k

##### See Also

nn2 for details on search algorithm

• knn
##### Examples
# NOT RUN {
library(sp)
data(meuse)
coordinates(meuse) <- ~x+y

idx <- sample(1:nrow(meuse), 10)
pts <- meuse[idx,]
meuse <- meuse[-idx,]
meuse\$IDS <- 1:nrow(meuse)

# Find 2 neighbors in meuse
( nn <- knn(pts, meuse, k=2, ids = "IDS", indexes = TRUE) )
plot(pts, pch=19, main="KNN")
points(meuse[nn[,1],], pch=19, col="red")

# Using covariates (weights)
wx = as.matrix(meuse@data[,1:3])
wy = as.matrix(pts@data[,1:3])

( nn <- knn(pts, meuse, k=2, ids = "IDS", indexes = TRUE,
weights.y=wy, weights.x=wx) )
plot(pts, pch=19, main="KNN")
points(meuse[nn[,1],], pch=19, col="red")

# Using coordinate matrices
y <- coordinates(pts)
x <- coordinates(meuse)
knn(y, x, k=2)

# }

Documentation reproduced from package spatialEco, version 1.3-2, License: GPL-3

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