pkdecompint {diffractometry}R Documentation

Decomposition of peaks in an interval

Description

Decomposition of peaks in an interval of the diffractogram

Usage

pkdecompint(baslfit, intnum, k, thresh=0, alpha=0.1, heterosk=TRUE,
maxiter=10000, dispers=1, baselim=c(0.05,5))

Arguments

baslfit Output of baslfit
intnum Number of interval
k Number of peak components to fit
thresh Threshold for residual criterion
alpha Test level for residual criterion
heterosk If TRUE, the estimate of noise level given in baslfit is used (default); otherwise noise level is taken to be proportional to signal height
maxiter Number of attempts to fit a model with k components
dispers Additional dispersion factor; not used if heterosk==T
baselim Limits for changes in the baseline estimate; first component is given in percent of the baseline height, second in counts/2theta

Value

Returns a LIST with components

intnr Number of interval
x values of 2theta
y the diffractogram with baseline removed
fit the resulting fit, evaluated at all points of x
fitpk a matrix with num.ker rows that contain fits of the individual peak components
basl the basline estimate as given in baslfit
baslchg chnage of baseline estimate
rss residual sum of squares, standardized by noise level estimate
num.ker number of peak components
par parameter vector as given in section 8 of Davies et al. (2008)
parbl intercept and slope of the baseline change
parpks physical characteristics of the peaks
accept is the fit accepted by the residual criterion
alpha test level for residual criterion
thresh threshold used in residual criterion

Author(s)

T. Mildenberger; Algorithm for residual criterion by T. Bernholt and T. Hofmeister

References

P.L. Davies, U. Gather, M. Meise, D. Mergel, T. Mildenberger (2008): "Residual based localization and quantification of peaks in x-ray diffractograms", to appear in the Annals of Applied Statistics. http://arxiv.org/abs/0711.3687

T. Bernholt and T. Hofmeister (2006): "An algorithm for a generalized maximum subsequence problem", in: J. Correa, A. Hevia, M. Kiwi (editors), "Latin 2006: Theoretical Informatics", volume 3887 of Lecture notes in Computer Science, pages 178-189, Berlin, Heidelberg. Springer Verlag

See Also

diffractogram, baselinefit, pkdecomp

Examples

## Decomposition of data in peak interval into two components

par(mfrow=c(2,1))

data(indiumoxide)
indox<-indiumoxide[1901:2400,]
base<-baselinefit(indox)

ind<-c(base$indlsep[1],base$indrsep[1])

plot(indox[ind[1]:ind[2],1], 
base$baseline$peaks[ind[1]:ind[2]],xlab="",ylab="")

pks<-pkdecompint(base,intnum=1,k=2)

lines(indox[ind[1]:ind[2],1],pks$fit,col="red")
plot(indox[ind[1]:ind[2],1],pks$fitpk[1,],ylim=c(0,1800),type="l",xlab="",ylab="")
lines(indox[ind[1]:ind[2],1],pks$fitpk[2,])


[Package diffractometry version 0.1-00 Index]