# NOT RUN {
data(Atrazine)
cenfit(Atrazine$Atra, Atrazine$AtraCen)
cenfit(Atrazine$Atra, Atrazine$AtraCen, Atrazine$Month)
cenfit(Cen(Atrazine$Atra, Atrazine$AtraCen))
cenfit(Cen(Atrazine$Atra, Atrazine$AtraCen)~Atrazine$Month)
# }
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