IsoplotR (version 0.11)

isochron: Calculate and plot isochrons

Description

Plots cogenetic \(^{40}\)Ar/\(^{39}\)Ar data as X-Y scatterplots, fits an isochron curve through them using the yorkfit function, and computes the corresponding isochron age, including decay constant uncertainties.

Usage

isochron(x, ...)
# S3 method for default
isochron(x, xlim = NA, ylim = NA, alpha = 0.05,
  sigdig = 2, show.numbers = FALSE, ellipse.col = rgb(0, 1, 0, 0.5),
  line.col = "red", lwd = 2, title = TRUE, ...)
# S3 method for ArAr
isochron(x, xlim = NA, ylim = NA, alpha = 0.05,
  sigdig = 2, show.numbers = FALSE, ellipse.col = rgb(0, 1, 0, 0.5),
  inverse = TRUE, line.col = "red", lwd = 2, plot = TRUE,
  exterr = TRUE, ...)
# S3 method for RbSr
isochron(x, xlim = NA, ylim = NA, alpha = 0.05,
  sigdig = 2, show.numbers = FALSE, ellipse.col = rgb(0, 1, 0, 0.5),
  line.col = "red", lwd = 2, plot = TRUE, exterr = TRUE, ...)
# S3 method for ReOs
isochron(x, xlim = NA, ylim = NA, alpha = 0.05,
  sigdig = 2, show.numbers = FALSE, ellipse.col = rgb(0, 1, 0, 0.5),
  line.col = "red", lwd = 2, plot = TRUE, exterr = TRUE, ...)
# S3 method for SmNd
isochron(x, xlim = NA, ylim = NA, alpha = 0.05,
  sigdig = 2, show.numbers = FALSE, ellipse.col = rgb(0, 1, 0, 0.5),
  line.col = "red", lwd = 2, plot = TRUE, exterr = TRUE, ...)

Arguments

x

EITHER a matrix with the following five columns:

X

the x-variable

sX

the standard error of X

Y

the y-variable

sY

the standard error of Y

rXY

the correlation coefficient of X and Y

OR

an object of class ArAr, ReOs, RbSr or SmNd

...

optional arguments

xlim

2-element vector with the plot limits of the x-axis

ylim

2-element vector with the plot limits of the y-axis

alpha

confidence cutoff for the error ellipses

sigdig

the number of significant digits of the numerical values reported in the title of the graphical output

show.numbers

logical flag (TRUE to show grain numbers)

ellipse.col

background colour of the error ellipses

line.col

colour of the isochron line

lwd

line width

title

add a title to the plot?

inverse

if TRUE, plots \(^{36}\)Ar/\(^{40}\)Ar vs. \(^{39}\)Ar/\(^{40}\)Ar. If FALSE, plots \(^{40}\)Ar/\(^{36}\)Ar vs. \(^{39}\)Ar/\(^{36}\)Ar.

plot

if FALSE, suppresses the graphical output

exterr

propagate external sources of uncertainty (J, decay constant)?

Value

if plot=FALSE, returns a list with the following items:

a

the intercept of the straight line fit and its standard error

b

the slope of the fit and its standard error

y0

this either equals a or, if x has class ArAr, the atmospheric \(^{40}\)Ar/\(^{36}\)Ar ratio and its standard error

age

the \(^{40}\)Ar/\(^{39}\)Ar, Re-Os, Rb-Sr or Sm-Nd age and its standard error

Examples

data(examples)
isochron(examples$ArAr)