NADA2 (version 1.0.1)

bestaic: Find the lowest AIC multiple regression model

Description

Computes (2^k-1) censored regression models and their AIC statistics. Prints out the lowest AIC models and the terms used.

Usage

bestaic(y.var, cen.var, x.vars, LOG = TRUE, n.models = 10)

Arguments

y.var

The column of y (response variable) values plus detection limits.

cen.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 is in y.var.

x.vars

One or more uncensored explanatory variable(s). See Details

LOG

Indicator of whether to compute the regression in the original y units, or on their logarithms. The default is to use the logarithms (LOG = TRUE). To compute in original units, specify the option LOG = FALSE (or LOG = 0).

n.models

The number of models with their AIC values to be printed in the console window. All (2^k-1) models are computed internally. This sets how many "best" (lowest AIC) models have output printed to the console.

Value

Prints number of x.vars, lists x.vars and AIC values.

Details

x.vars: If 1 x variable only, enter its name. If multiple x variables, enter the name of a data frame of columns of the x variables. No extra columns unused in the regression allowed. Create this by x.frame <- data.frame (Temp, Flow, Time) for 3 variables (temperature, flow and time).

AIC of each model is printed from lowest to highest AIC to help evaluate the <U+2018>best<U+2019> regression model. n.models determines how many lines of model info is printed.

LOG: The default is that the Y variable will be log transformed (LOG = TRUE).

References

Helsel, D.R., 2011. Statistics for censored environmental data using Minitab and R, 2nd ed. John Wiley & Sons, USA, N.J.

See Also

survival::survreg

Examples

# NOT RUN {
data(Brumbaugh)

# Multiple regression
bestaic(Brumbaugh$Hg, Brumbaugh$HgCen, Brumbaugh[, c("SedMeHg","PctWetland", "SedAVS")])
# }