numOSL (version 1.5)

decompc: Decomposing an OSL decay curve (allows a constant component being subtracted)

Description

Decomposing an OSL decay curve (type "CW" or "LM") to a specified number of components (plus a constant component).

Usage

decompc(Sigdata, ncomp = 2, typ = c("cw", "lm"), 
        control.args = list(), LEDpower = 60, LEDwavelength = 470, 
        plot = TRUE, xlog = TRUE, lwd = 3, samplename = NULL, outfile = NULL)

Arguments

Sigdata

data.frame(required): two columns, i.e. time values (t1,t2,etc) and signal values (s1,s2,etc)

ncomp

numeric(with default): the number of components to be decomposed, which should be an integer from the space [1,7]

typ

character(with default): the type ("cw" or "lm") of an OSL decay curve, default typ="cw"

control.args

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

LEDpower

numeric(with default): the LED power (mW/cm2) used in the measurement

LEDwavelength

numeric(with default): the wavelength (nm) used in the measurement

plot

logical(with default): plot the fitted results or not

xlog

logical(with default): use a log-scale x-axis for plotting or not

lwd

numeric(with default): the width of curves in the plot

samplename

character(optional): the name of the sample

outfile

character(optional): if specified, decomposed signal values will be written to a file named "outfile" in ".csv" format and will be saved to the current work directory

Value

• Return an invisible list containing following elements:
• Comp.Signal
  the fitted decaying signals for each component
• pars
  the estimates and associated standard errors
• constant
  the estimated constant component
• value
  the sum of squared residuals
• errorflag
  an error message generated during the calculation, if parameters' standard errors are available, errorflag=0, or else errorflag=1

Details

Function decompc() is used to decompose a decay curves with a subtracted constant component (a constant component may be regarded as the sum of decaying signals of some slower components plus the background). For a CW-OSL decay curves: I(t)=a1*b1*exp(-b1*t)+a2*b2*exp(-b2*t)+...+ak*bk*exp(-bk*t)+c , k=1, 2, ..., 7, And for LM-OSL decay curves: I(t)=a1*b1*(t/P)*exp(-b1*t^2/(2*P))+a2*b2*(t/P)*exp(-b2*t^2/(2*P))+...+ ak*bk*(t/P)*exp(-bk*t^2/(2*P))+c*(t/P) , k=1, 2, ..., 7 Note that unlike function decomp(), the fitting model is different and a transformation (transf) of parameters is not allowed here. For more details, see function decomp.

See Also

decomp; fastED

Examples

data(Signaldata)
  res<-decompc(Signaldata$lm,ncomp=4,typ="lm")
  list(res$pars,res$constant)