feature_UGFS: Unsupervised Graph-based Feature Selection

In Rdimtools: Dimension Reduction and Estimation Methods

Unsupervised Graph-based Feature Selection

Description

UGFS is an unsupervised feature selection method with two parameters nbdk and varthr that it constructs an affinity graph using local variance computation and scores variables based on PageRank algorithm.

Usage

do.ugfs(
  X,
  ndim = 2,
  nbdk = 5,
  varthr = 2,
  preprocess = c("null", "center", "scale", "cscale", "whiten", "decorrelate")
)

Arguments

X	an (n\times p) matrix or data frame whose rows are observations and columns represent independent variables.
ndim	an integer-valued target dimension.
nbdk	the size of neighborhood for local variance computation.
varthr	threshold value for affinity graph construction. If too small so that the graph of variables is not constructed, it returns an error.
preprocess	an additional option for preprocessing the data. Default is "null". See also aux.preprocess for more details.

Value

a named list containing

Y

an (n\times ndim) matrix whose rows are embedded observations.

prscore

a length-p vector of score computed from PageRank algorithm. Indices with largest values are selected.

featidx

a length-ndim vector of indices with highest scores.

trfinfo

a list containing information for out-of-sample prediction.

projection

a (p\times ndim) whose columns are basis for projection.

Author(s)

Kisung You

References

\insertRef

henni_unsupervised_2018Rdimtools

Examples

## use iris data
## it is known that feature 3 and 4 are more important.
data(iris)
iris.dat <- as.matrix(iris[,1:4])
iris.lab <- as.factor(iris[,5])

## try multiple thresholding values
out1 = do.ugfs(iris.dat, nbdk=10, varthr=0.5)
out2 = do.ugfs(iris.dat, nbdk=10, varthr=5.0)
out3 = do.ugfs(iris.dat, nbdk=10, varthr=9.5)

## visualize
opar <- par(no.readonly=TRUE)
par(mfrow=c(1,3))
plot(out1$Y, pch=19, col=iris.lab, main="bandwidth=0.1")
plot(out2$Y, pch=19, col=iris.lab, main="bandwidth=1")
plot(out3$Y, pch=19, col=iris.lab, main="bandwidth=10")
par(opar)

Rdimtools documentation built on Dec. 28, 2022, 1:44 a.m.