EMMAgeo (version 0.9.4)

get.limits: Create lower and upper mode position limits to define robust end-members.

Description

This function identifies the lower and upper limits within which robust end-members have clustered mode positions. It uses a kernel density estimate of the mode positions of all input end-member loadings, clips it at a user-defined minimum density and returns the resulting rising and falling shoulders of the kde peaks as limits.

Usage

get.limits(loadings, bw, threshold = 0.7)

Arguments

loadings

Numeric matrix with m loadings (rows) and n classes (columns).

bw

Numeric scalar, bandwidth of the kernel, which is moved over the data set. If omitted, the default value of 1 used.

threshold

Numeric scalar, threshold quantile which is used to identify mode clusters. Only kde densities above this values are kept and used to derieve mode cluster limits.

Value

Numeric matrix with lower and upper mode limits.

Details

Note that the threshold above which a mode cluster is identified is an arbitrary, user-defined value and probably needs to be adjusted iteratively to get reasonable results. The default value may or may not be adequate!

References

Dietze E, Hartmann K, Diekmann B, IJmker J, Lehmkuhl F, Opitz S, Stauch G, Wuennemann B, Borchers A. 2012. An end-member algorithm for deciphering modern detrital processes from lake sediments of Lake Donggi Cona, NE Tibetan Plateau, China. Sedimentary Geology 243-244: 169-180.

See Also

EMMA, model.em

Examples

# NOT RUN {
## load example data set
data(X, envir = environment())

## define parameters
l <- c(0, 0.1)
q <- rbind(c(2, 3),
           c(3, 4))

## model all possible end-members
em.pot <- model.em(X = X,
                   q = q,
                   l = l)

## infer mode cluster limits
limits <- get.limits(loadings = em.pot$loadings)
# }