cenQQ function

Q-Q Plot censored data

Plots a quantile-quantile (Q-Q) plot of censored data versus a fitted data distribution

cenQQ(x.var, cens.var, dist = "lnorm", Yname = yname)

Arguments

• x.var: The column of x (response variable) values plus detection limits
• cens.var: The column of indicators, where 1 (or TRUE) indicates a detection limit in the y.var column, and 0 (or FALSE) indicates a detected value in y.var.
• dist: One of three distributional shapes to fit to your data: lognormal (lnorm), normal (norm) or gamma (gamma).
• Yname: Optional – input text in quotes to be used as the variable name on the Q-Q plot. The default is the Yname name of the y.var input variable.

Returns

A single Q-Q plot of data fitted by normal, lognormal or gamma distributions with Shapiro-Francia W value printed on plot.

Examples

data(Brumbaugh)
cenQQ(Brumbaugh$Hg,Brumbaugh$HgCen)

# User defined distribution
cenQQ(Brumbaugh$Hg,Brumbaugh$HgCen,dist="gamma")

References

Helsel, D.R., 2011. Statistics for Censored Environmental Data using Minitab and R, 2nd ed. John Wiley & Sons, USA, N.J.

Shapiro, S.S., Francia, R.S., 1972. An approximate analysis of variance test for normality. Journal of the American Statistical Association 67, 215–216.