fit_ThermalQuenching: Fitting Thermal Quenching Data

In Luminescence: Comprehensive Luminescence Dating Data Analysis

Fitting Thermal Quenching Data

Description

Applying a nls-fitting to thermal quenching data.

Usage

fit_ThermalQuenching(
  data,
  start_param = list(),
  method_control = list(),
  n.MC = 100,
  verbose = TRUE,
  plot = TRUE,
  ...
)

Arguments

data	data.frame (required): input data with three columns, the first column contains temperature values in deg. C, columns 2 and 3 the dependent values with its error
start_param	list (optional): option to provide the start parameters for the fitting, see details
method_control	list (optional): further options to fine tune the fitting, see details for further information
n.MC	numeric (with default): number of Monte Carlo runs for the error estimation. If n.MC is NULL or ⁠<=1⁠, the error estimation is skipped
verbose	logical (with default): enable/disable output to the terminal.
plot	logical (with default): enable/disable the plot output.
...	further arguments that can be passed to control the plotting, support are main, pch, col_fit, col_points, lty, lwd, xlab, ylab, xlim, ylim, xaxt

Details

Used equation

The equation used for the fitting is

y = (A / (1 + C * (exp(-W / (k * x))))) + c

W is the energy depth in eV and C is dimensionless constant. A and c are used to adjust the curve for the given signal. k is the Boltzmann in eV/K and x is the absolute temperature in K.

Error estimation

The error estimation is done be varying the input parameters using the given uncertainties in a Monte Carlo simulation. Errors are assumed to follow a normal distribution.

start_param

The function allows the injection of own start parameters via the argument start_param. The parameters needs to be provided as names list. The names are the parameters to be optimised. Examples: start_param = list(A = 1, C = 1e+5, W = 0.5, c = 0)

method_control

The following arguments can be provided via method_control. Please note that arguments provided via method_control are not further tested, i.e., if the function crashes your input was probably wrong.

ARGUMENT	TYPE	DESCRIPTION
upper	named vector	sets upper fitting boundaries, if provided boundaries for all arguments are required, e.g., c(A = 0, C = 0, W = 0, c = 0)
lower	names vector	set lower fitting boundaries (see upper for details)
trace	logical	enable/disable progression trace for minpack.lm::nlsLM
weights	numeric	option to provide own weights for the fitting, the length of this vector needs to be equal to the number for rows of the input data.frame. If set to NULL no weights are applied. The weights are defined by the third column of the input data.frame.

Value

The function returns numerical output and an (optional) plot.

———————————–
⁠[ NUMERICAL OUTPUT ]⁠
———————————–

RLum.Results-object

slot: ⁠@data⁠

⁠[.. $data : data.frame]⁠

A table with all fitting parameters and the number of Monte Carlo runs used for the error estimation.

⁠[.. $fit : nls object]⁠

The nls stats::nls object returned by the function minpack.lm::nlsLM. This object can be further passed to other functions supporting an nls object (cf. details section in stats::nls)

slot: ⁠@info⁠

⁠[.. $call : call]⁠

The original function call.

———————————–
⁠[ GAPHICAL OUTPUT ]⁠
———————————–

Plotted are temperature against the signal and their uncertainties. The fit is shown as dashed-line (can be modified). Please note that for the fitting the absolute temperature values are used but are re-calculated to deg. C for the plot.

Function version

0.1.0

How to cite

Kreutzer, S., 2025. fit_ThermalQuenching(): Fitting Thermal Quenching Data. Function version 0.1.0. In: Kreutzer, S., Burow, C., Dietze, M., Fuchs, M.C., Schmidt, C., Fischer, M., Friedrich, J., Mercier, N., Philippe, A., Riedesel, S., Autzen, M., Mittelstrass, D., Gray, H.J., Galharret, J., Colombo, M., Steinbuch, L., Boer, A.d., 2025. Luminescence: Comprehensive Luminescence Dating Data Analysis. R package version 1.0.1. https://r-lum.github.io/Luminescence/

Author(s)

Sebastian Kreutzer, Institute of Geography, Heidelberg University (Germany) , RLum Developer Team

References

Wintle, A.G., 1975. Thermal Quenching of Thermoluminescence in Quartz. Geophys. J. R. astr. Soc. 41, 107–113.

See Also

minpack.lm::nlsLM

Examples

##create short example dataset
data <- data.frame(
  T = c(25, 40, 50, 60, 70, 80, 90, 100, 110),
  V = c(0.06, 0.058, 0.052, 0.051, 0.041, 0.034, 0.035, 0.033, 0.032),
  V_X = c(0.012, 0.009, 0.008, 0.008, 0.007, 0.006, 0.005, 0.005, 0.004))

##fit
fit_ThermalQuenching(
 data = data,
 n.MC = NULL)

Luminescence documentation built on April 3, 2025, 7:52 p.m.