# zerodist

From sp v1.0-2
0th

Percentile

##### find point pairs with equal spatial coordinates

find point pairs with equal spatial coordinates

Keywords
dplot
##### Usage
zerodist(obj, zero = 0.0, unique.ID = FALSE)
zerodist2(obj1, obj2, zero = 0.0)
remove.duplicates(obj, zero = 0.0, remove.second = TRUE)
##### Arguments
obj
object of, or extending, class SpatialPoints
obj1
object of, or extending, class SpatialPoints
obj2
object of, or extending, class SpatialPoints
zero
distance values less than or equal to this threshold value are considered to have zero distance (default 0.0)
unique.ID
logical; if TRUE, return an ID (integer) for each point that is different only when two points do not share the same location
remove.second
logical; if TRUE, the second of each pair of duplicate points is removed, if FALSE remove the first
##### Value

• zerodist and zerodist2 return a two-column matrix with in each row pairs of row numbers with identical coordinates; a matrix with zero rows is returned if no such pairs are found. For zerodist, row number pairs refer to row pairs in obj. For zerodist2, row number pairs refer to rows in obj and obj2, respectively. remove.duplicates removes duplicate observations if present, and else returns obj.

##### Note

When using kriging, duplicate observations sharing identical spatial locations result in singular covariance matrices. This function may help identify and remove spatial duplices. The full matrix with all pair-wise distances is not stored; the double loop is done at the C level.

##### Aliases
• zerodist
• zerodist2
• remove.duplicates
##### Examples
data(meuse)
summary(meuse)
# pick 10 rows
n <- 10
ran10 <- sample(nrow(meuse), size = n, replace = TRUE)
meusedup <- rbind(meuse, meuse[ran10, ])
coordinates(meusedup) <- c("x", "y")
zd <- zerodist(meusedup)
sum(abs(zd[1:n,1] - sort(ran10))) # 0!
# remove the duplicate rows:
meusedup2 <- meusedup[-zd[,2], ]
summary(meusedup2)
meusedup3 <- subset(meusedup, !(1:nrow(meusedup) %in% zd[,2]))
summary(meusedup3)
coordinates(meuse) <- c("x", "y")
zerodist2(meuse, meuse[c(10:33,1,10),])
Documentation reproduced from package sp, version 1.0-2, License: GPL (>= 2)

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