proxi: Proximity Function

In ICGE: Estimation of Number of Clusters and Identification of Atypical Units

Proximity Function

Description

Assume that n units are divided into k groups C1,...,Ck. The function calculates the proximity function from a specific unit x0 to the groups Cj.

Usage

proxi(d, dx0, pert = "onegroup")

Arguments

d	a distance matrix or a dist object with distance information between units.
dx0	an n-vector containing the distances from x0 to the other units.
pert	an n-vector that indicates which group each unit belongs to. Note that the expected values of pert are numbers greater than or equal to 1 (for instance 1,2,3,4..., k). The default value indicates there is only one group in data.

Value

k-vector containing the proximity function value from x0 to each group.

Author(s)

Itziar Irigoien [e-mail]; Konputazio Zientziak eta Adimen Artifiziala, Euskal Herriko Unibertsitatea (UPV/EHU), Donostia, Spain.

Conchita Arenas [e-mail]; Departament d'Estadistica, Universitat de Barcelona, Barcelona, Spain.

References

Arenas, C. and Cuadras, C.M. (2002). Some recent statistical methods based on distances. Contributions to Science, 2, 183–191.

Cuadras, C.M., Fortiana, J. and Oliva, F. (1997). The proximity of an individual to a population with applications in discriminant analysis. Journal of Classification, 14, 117–136.

See Also

vgeo, deltas

Examples

data(iris)
d <- dist(iris[,1:4])

# xo contains a unit from one group, as for example group 1.
x0 <- c(5.3, 3.6, 1.1, 0.1) 
# distances between x0 and the other units.
dx0 <- rep(0,150)
for (i in 1:150){
	dif <-x0-iris[i,1:4]
	dx0[i] <- sqrt(sum(dif*dif))
}

proxi(d, dx0, iris[,5])


# xo contains a unit from one group, as for example group 2.
x0 <- c(6.4, 3.0, 4.8, 1.3) 
# distances between x0 and the other units.
dx0 <- rep(0,150)
for (i in 1:150){
	dif <-x0-iris[i,1:4]
	dx0[i] <- sqrt(sum(dif*dif))
}

proxi(d, dx0, iris[,5])

ICGE documentation built on Oct. 17, 2022, 5:10 p.m.