This function uses the input data matrix X and a vector of weight
transformation limits to generate a matrix of minimum and maximum likely
numbers of end-members to be used to model and extract robust end-members.
get.q(
X,
l = 0,
q.min = 2,
q.max = 10,
criteria.min = 0.5,
criteria.max = "local_max",
correct.output = TRUE,
...
)Numeric matrix, input data set with m samples (rows)
and n variables (columns).
Numeric vector, weight transformation limits, default
is zero.
Numeric scalar, minimum number of end-members to use,
default is 2.
Numeric scalar, maximum number of end-members to use,
default is 10.
Numeric scalar, minimum value of explained
variance reached to be a valid model realisation, default is 0.5.
Character or numeric scalar, either keyword
"local_max" to use first local maximum or any numeric value of
explained variance, default is "local_max".
Logical scalar, option to correct the output
for twisted values and remove combinations with NA-values. See details.
Further arguments, passed to the function.
Numeric matrix of class "EMMAgeo_q", minimum and
maximum numbers of end-members as well as corresponding weight
transformation values as rownames.
The parameter q.min should be at least 2 because otherwise the
entire dataset would consist of one end-member and there would be no
variability at all. The parameter q.max is set to 10 by default,
based on practical issues. In natural systems, there are only rarely
occasions when such a high number of sediment transport regimes may be
preserved in and can be resolved from sedimentary deposits. The parameter
l should be a vector between the minimum possible (zero) and maximum
possible value (by definition the median, 0.5, but usually a lower value).
Whensubmitting only a scalar, the variability can be only due to the range
of possible endmembers (between q.min and q.max). If the
parameter correct.output is enabled, this can decrease the number of
valid values for l, i.e. the number of rows of the output matrix
may no longer be the same as the length of the input vector of l. In
such a case the vector l must be replaced by the rownames of the
output matrix (l <- as.numeric(rownames(get.q()))).
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.
# NOT RUN {
## load example data set
data("example_X")
## create parameter matrix
get.q(X = X, l = c(0, 0.05, 0.10, 0.15))
# }
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