IsoplotR (version 0.18)

ludwig: Linear regression of X,Y,Z-variables with correlated errors, taking into account decay constant uncertainties.

Description

Implements the maximum likelihood algorithm of Ludwig (1998)

Usage

ludwig(x, ...)
# S3 method for default
ludwig(x, ...)
# S3 method for UPb
ludwig(x, exterr = FALSE, alpha = 0.05, ...)

Arguments

x

an object of class UPb

...

optional arguments

exterr

propagate external sources of uncertainty (e.g., decay constant)?

alpha

cutoff value for confidence intervals

Value

par

a two-element vector with the lower concordia intercept and initial \(^{207}\)Pb/\(^{206}\)Pb-ratio.

cov

the covariance matrix of par

df

the degrees of freedom of the model fit (\(3n-3\), where \(n\) is the number of aliquots).

mswd

the mean square of weighted deviates (a.k.a. reduced Chi-square statistic) for the fit.

p.value

p-value of a Chi-square test for the linear fit

References

Ludwig, K.R., 1998. On the treatment of concordant uranium-lead ages. Geochimica et Cosmochimica Acta, 62(4), pp.665-676.

Examples

# NOT RUN {
f <- system.file("UPb4.csv",package="IsoplotR")
d <- read.data(f,method="U-Pb",format=4)
fit <- ludwig(d)
# }