Computes the ATS (Mann-Kendall trend test for censored data) after adjustment of censored data for a covariate.
centrend( y.var, y.cens, x.var, time.var, link = "identity", Smooth = "cs", printstat = TRUE, stackplots = FALSE )
The column of y (response variable) values plus detection limits
The column of indicators, where 1 (or
TRUE) indicates a detectionlimit in the
y.var column, and 0 (or
FALSE) indicates a detected value in
Column of a covariate (not time).
y.var will be smoothed versus
x.var and residuals taken to subtract out the relationship between
Column of the time variable, either a sequence of days or decimal times, etc. Will be the scale used for time in ATS trend analysis.
“identity” which means it uses data in the original units. See details.
Type of smoother used in the GAM. Default is
“cs”, shrinkage cubic regression splines. See details for other options.
FALSE option of whether to print the resulting statistics in the console window, or not. Default is
logical 'TRUE'/'FALSE' option to stack three plots that are output onto the same page instead of each on separate page. Default is 'FALSE', each separate.
Prints three plots: Y data vs time with GAM Smooth, Residuals from GAM Smooth vs time, and ATS trend line of residuals vs time.
Returns GAM residuals and ATS results on trend test of residuals (intercept, slope, Kendall's tau, p-value for trend)
link = identity. The y variables are then used in their original units. Other options are available see
cenGAM::tobit1 for more options.
"cs" for shrinkage cubic regression splines. See
mgcv::smooth.terms for other types of smoothing algorithms. '"ts"' is a thin-plate regression spline and is also commonly used.
Helsel, D.R., 2011. Statistics for censored environmental data using Minitab and R, 2nd ed. John Wiley & Sons, USA, N.J.