numOSL (version 1.0)

fastED: Estimating a fast-component equivalent dose in OSL dating

Description

With the data obtained by single aliquot regenerative (SAR) protocol (Murray and Wintle, 2000), a series decay curves are decomposed and signals of fast-component are extracted (if possible) to build a dose response curve to approximate a fast-component equivalent dose.

Usage

fastED(Sigdata, Redose, ncomp = 2, constant=TRUE,  
       control.args = list(), typ = "cw", nstart = 100,  
       upb = 1, ErrorMethod = c("mc", "sp"), origin = NULL)

Arguments

Sigdata

data.frame(required): a series of decay curves obtained with SAR method, the first column of which must be time values and at least a total of five columns must be provided

Redose

vector(required): regenerative dose values, such as redose1, redose2, etc

ncomp

numeric(with default): number of components used to decompose each decay curve, which must be an integer in the range [2,4]

constant

logical(with default): subtract a constant in curve decomposition or not

control.args

list(with default): further arguments used in differential evolution algorithm, see decomp

typ

character(with default): type of the OSL decay curve, only type of "CW" is available currently

nstart

numeric(with default): maximum number of attempts that used to initialize parameters in dose response curve fitting, see calED

upb

numeric(with default): upper boundary of b value, initial b values will be generated uniformly from (0, upb), see calED

ErrorMethod

character(with default): method ("sp" or "mc") for estimating the standard error of equivalent dose. Default ErrorMethod="mc". See calED

origin

logical(optional): whether force the fitting to pass the origin (x=0,y=0) or not, see calED

Value

• Return a list containing following elements:
• pars
  estimated parameters and associated standard errors for each decay curve
• decayRate
  summarized list about all decay rates (if zero regenerative dose appears, the corresponded decay rates will be precluded in the calculation)
• Curvedata
  data used to build a dose response curve, see calED
• Lxt
  standardized natural signal and its standard error, see calED
• model
  model used for fitting the dose-response curve, which is chosen automatically from "line", "exp" or "line+exp" during the calculation
• LMpars
  characteristic parameters and standard errors of the dose-response curve
• residual
  sum of square of residual errors for the fitted dose response curve
• ED
  estimated equivalent dose (and corresponded standard error)
• RecyclingRatio
  estimated recycling ratio
• Recuperation
  estimated recuperation

Details

Function fastED() is used to estimated a fast-component equivalent dose with data obtained by the SAR protocol (Murray and Wintle, 2000), only CW-OSL data can be analyzed currently. The routine trys to decompose a series of decay curves to a specified number of components, then the fast-component signal from each decay curve will be extracted to build the dose response curve, from which a fast-component equivalent dose could be obtained.

References

Murray, A.S., Wintle, A.G., 2000. Luminescence dating of quartz using improved single-aliquot regenerative-dose protocol. Radiation Measurements, 32, pp.57-73.

Li, S.H., Li, B., 2006. Dose measurement using the fast component of LM-OSL signals from quartz. Radiation Measurements, 41, pp.534-541.

See Also

calED; decomp; decompc

Examples

# Loading signal data
 data(Signaldata)
# Calculating a fast-component dose with three components after removing the 
# decay curves that correspond to zero-redose (12th) and its test-dose (13th)
 fastED(Signaldata$cw[,c(-12,-13)],Redose=c(80,160,240,320,80)*0.13,
        ncomp=3,constant=FALSE)
# Trying with two component plus a constant
 fastED(Signaldata$cw,Redose=c(80,160,240,320,0,80)*0.13,ncomp=2)