diff options
Diffstat (limited to 'man/massart97ex3.Rd')
-rw-r--r-- | man/massart97ex3.Rd | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/man/massart97ex3.Rd b/man/massart97ex3.Rd new file mode 100644 index 0000000..efdcf02 --- /dev/null +++ b/man/massart97ex3.Rd @@ -0,0 +1,51 @@ +\name{massart97ex3} +\docType{data} +\alias{massart97ex3} +\title{Calibration data from Massart et al. (1997), example 3} +\description{ + Sample dataset from p. 188 to test the package. +} +\usage{data(massart97ex3)} +\format{ + A dataframe containing 6 levels of x values with 5 + observations of y for each level. +} +\examples{ +data(massart97ex3) +attach(massart97ex3) +yx <- split(y, x) +ybar <- sapply(yx, mean) +s <- round(sapply(yx, sd), digits = 2) +w <- round(1 / (s^2), digits = 3) +weights <- w[factor(x)] +m <- lm(y ~ x, w = weights) +calplot(m) + +# The following concords with the book p. 200 +inverse.predict(m, 15, ws = 1.67) # 5.9 +- 2.5 +inverse.predict(m, 90, ws = 0.145) # 44.1 +- 7.9 + +# The LOD is only calculated for models from unweighted regression +# with this version of chemCal +m0 <- lm(y ~ x) +lod(m0) + +# Limit of quantification from unweighted regression +loq(m0) + +# For calculating the limit of quantification from a model from weighted +# regression, we need to supply weights, internally used for inverse.predict +# If we are not using a variance function, we can use the weight from +# the above example as a first approximation (x = 15 is close to our +# loq approx 14 from above). +loq(m, w.loq = 1.67) +# The weight for the loq should therefore be derived at x = 7.3 instead +# of 15, but the graphical procedure of Massart (p. 201) to derive the +# variances on which the weights are based is quite inaccurate anyway. +} +\source{ + Massart, L.M, Vandenginste, B.G.M., Buydens, L.M.C., De Jong, S., Lewi, P.J., + Smeyers-Verbeke, J. (1997) Handbook of Chemometrics and Qualimetrics: Part A, + Chapter 8. +} +\keyword{datasets} |