IsoplotR (version 0.18)

agespectrum: Plot a (40Ar/39Ar) release spectrum

Description

Produces a plot of boxes whose widths correspond to the cumulative amount of \(^{39}\)Ar (or any other volume proxy), and whose heights express the analytical uncertainties. Only propagates the analytical uncertainty associated with decay constants and J-factors after computing the plateau composition.

Usage

agespectrum(x, ...)
# S3 method for default
agespectrum(x, alpha = 0.05, plateau = TRUE,
  plateau.col = rgb(0, 1, 0, 0.5), non.plateau.col = rgb(0, 1, 1, 0.5),
  sigdig = 2, line.col = "red", lwd = 2, title = TRUE,
  xlab = "cumulative fraction", ylab = "age [Ma]", ...)
# S3 method for ArAr
agespectrum(x, alpha = 0.05, plateau = TRUE,
  plateau.col = rgb(0, 1, 0, 0.5), non.plateau.col = rgb(0, 1, 1, 0.5),
  sigdig = 2, exterr = TRUE, line.col = "red", lwd = 2, i2i = FALSE,
  ...)

Arguments

x

a three-column matrix whose first column gives the amount of \(^{39}\)Ar in each aliquot, and whose second and third columns give the age and its uncertainty.

OR

an object of class ArAr

...

optional parameters to the generic plot function

alpha

the confidence limits of the error bars/boxes and confidence intervals.

plateau

logical flag indicating whether a plateau age should be calculated. If plateau=TRUE, the function will compute the weighted mean of the largest succession of steps that yield values passing the Chi-square test for age homogeneity. If TRUE, returns a list with plateau parameters.

plateau.col

the fill colour of the rectangles used to mark the steps belonging to the age plateau.

non.plateau.col

if plateau=TRUE, the steps that do NOT belong to the plateau are given a different colour.

sigdig

the number of significant digits of the numerical values reported in the title of the graphical output (only used if plateau=TRUE).

line.col

colour of the isochron line

lwd

line width

title

add a title to the plot?

xlab

x-axis label

ylab

y-axis label

exterr

propagate the external (decay constant and calibration factor) uncertainties?

i2i

`isochron to intercept': calculates the initial (aka `inherited', `excess', or `common') \(^{40}\)Ar/\(^{36}\)Ar ratio from an isochron fit. Setting i2i to FALSE uses the default values stored in settings('iratio',...)

Value

if plateau=TRUE, returns a list with the following items:

mean

a 3-element vector with:

x: the plateau mean

s[x]: the estimated standard deviation of x

ci[x]: the 100(1-\(\alpha\))% confidence interval of t for the appropriate degrees of freedom

disp

a 2-element vector with:

s: the standard deviation of the overdispersion

ci: the 100(1-\(\alpha\))% confidence interval of the overdispersion for the appropriate degrees of freedom

df

the degrees of freedom for the weighted mean plateau fit

mswd

the mean square of the weighted deviates of the plateau

p.value

the p-value of a Chi-square test with \(df=n-2\) degrees of freedom, where \(n\) is the number of steps in the plateau and 2 degrees of freedom have been removed to estimate the mean and the dispersion.

fract

the fraction of \(^{39}\)Ar contained in the plateau

tfact

the t-factor for df degrees of freedom evaluated at \(100(1-\alpha/2)\)% confidence

plotpar

plot parameters for the weighted mean, which are not used in the age spectrum

i

indices of the steps that are retained for the plateau age calculation

Examples

# NOT RUN {
data(examples)
agespectrum(examples$ArAr,ylim=c(0,80))
# }