calculateAges {NiLeDAM}

Calculate the ages from electron microprobe measurements.

Description

This function calculates the ages, confidence intervals and standard deviations from triplets (U,Th,Ph), obtained by electron microprobe, given together with corresponding errors.

Usage

calculateAges(measures, nloops = 1000, level = 0.05, verbose = TRUE, seed = NULL)

Arguments

measures

a data.frame object with one electron microprobe measurement by row and with columns U, corresponding error for U, Th, corresponding error for Th, Pb, corresponding error for Pb, all expressed in ppm. See an example with data(srilanka).

nloops

the number of Monte Carlo (MC) simulations used to estimate the confidence intervals for the ages. Default is 1000.

level

the level of significance of the confidence intervals for the ages. Default is 0.05.

verbose

logical; activates the verbose mode. Default is TRUE.

seed

if supplied, initialize the random seed. Default is NULL (the random seed is not initialized).

Details

The ages are calculated by solving the Equation (1) of Montel et al. (1996). The equation is solved by the Broyden method implemented in the nleqslv() function.

The standard deviations and the confidence intervals are calculated using a MC approach: randomized observations of the triplets are generated from normal distributions with standard deviations equal to \frac{\textrm{error}}{2} where 'error' denotes the error in the measurement of Th, U or Pb, passed in measures. Standard deviations are estimated by the empirical standard deviations and confidence intervals by quantiles for probabilities \frac{\textrm{\texttt{level}}}{2} and 1-\frac{\textrm{\texttt{level}}}{2}, respectively.

Value

An object of class ages.

Note

You should use at least 1000 MC simulations otherwise the estimated confidence intervals and standard deviations will not be reliable. Such simulations can take a few seconds/minutes for fifty or so triplets and corresponding errors.

Author(s)

Jean-Marc Montel, [e-mail]

Nathalie Vialaneix, [e-mail]

References

Montel J.M., Foret S., Veschambre M., Nicollet C., Provost A. (1996) Electron microprobe dating of monazite. Chemical Geology, 131, 37–53.

See Also

ages tests

Examples

## Load the data
data(srilanka)

## Calculate the ages
calculateAges(srilanka, nloops=10)