Description Usage Arguments Details Value See Also Examples

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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | ```
agespectrum(x, ...)
## Default S3 method:
agespectrum(x, alpha = 0.05, plateau = TRUE,
random.effects = TRUE, levels = NA, clabel = "",
plateau.col = c("#00FF0080", "#FF000080"),
non.plateau.col = "#00FFFF80", sigdig = 2, line.col = "red",
lwd = 2, xlab = "cumulative fraction", ylab = "age [Ma]",
hide = NULL, omit = NULL, ...)
## S3 method for class 'ArAr'
agespectrum(x, alpha = 0.05, plateau = TRUE,
random.effects = TRUE, levels = NA, clabel = "",
plateau.col = c("#00FF0080", "#FF000080"),
non.plateau.col = "#00FFFF80", sigdig = 2, exterr = TRUE,
line.col = "red", lwd = 2, i2i = FALSE, hide = NULL,
omit = NULL, ...)
``` |

`x` |
a three-column matrix whose first column gives the amount of
OR an object of class |

`...` |
optional parameters to the generic |

`alpha` |
the confidence level of the error bars/boxes and confidence intervals. |

`plateau` |
logical flag indicating whether a plateau age should
be calculated. If |

`random.effects` |
if if |

`levels` |
a vector with additional values to be displayed as different background colours of the plot symbols. |

`clabel` |
label of the colour legend |

`plateau.col` |
Fill colours of the rectangles used to mark the steps belonging to
the age plateau. This can either be a single colour or multiple
colours to form a colour ramp (to be used if a single colour: multiple colours: a colour palette: a reversed palette: For empty boxes, set |

`non.plateau.col` |
if |

`sigdig` |
the number of significant digits of the numerical values reported in the title of the graphical output. |

`line.col` |
colour of the average age line |

`lwd` |
width of the average age line |

`xlab` |
x-axis label |

`ylab` |
y-axis label |

`hide` |
vector with indices of aliquots that should be removed from the plot. |

`omit` |
vector with indices of aliquots that should be plotted but omitted from age plateau calculation |

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

`i2i` |
‘isochron to intercept’: calculates the initial (aka
‘inherited’, ‘excess’, or ‘common’) |

`IsoplotR`

defines the ‘plateau age’ as the weighted mean age
(using a random effects model with two sources of dispersion) of
the longest sequence (in terms of cumulative *^{39}*Ar content)
of consecutive heating steps that pass the modified Chauvenet
criterion (see `weightedmean`

). Note that this
definition is different (and simpler) than the one used by
`Isoplot`

(Ludwig, 2003). However, it is important to mention
that all definitions of an age plateau are heuristic by nature and
should not be used for quantitative inference. It is possible (and
likely) that the plateau steps exhibit significant
overdispersion. This overdispersion can be manually reduced by
removing individual heating steps with the optional `omit`

argument.

If `plateau=TRUE`

, returns a list with the following items:

- mean
a 3-element vector with:

`x`

: the plateau mean`s[x]`

: the standard error of`x`

`ci[x]`

: the width of a 100(1-*α*)% confidence interval of`t`

- disp
a 3-element vector with:

`w`

: the overdispersion, i.e. the standard deviation of the Normal distribution that is assumed to describe the true ages.`ll`

: the width of the lower half of a 100(1-*α*)% confidence interval for the overdispersion`ul`

: the width of the upper half of a 100(1-*α*)% confidence interval for the overdispersion- 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- plotpar
plot parameters for the weighted mean (see

`weightedmean`

)- i
indices of the steps that are retained for the plateau age calculation

1 2 3 4 5 6 | ```
data(examples)
par(mfrow=c(2,1))
agespectrum(examples$ArAr)
# removing the first 6 steps yields the longest plateau
# that passes the chi-square test for homogeneity
agespectrum(examples$ArAr,omit=1:6)
``` |

pvermees/IsoplotR documentation built on Dec. 3, 2019, 6:25 a.m.

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