data(Morwong4a)
str(Morwong4a)
head(Morwong4a)
## extract aged sample
m4a.aged <- subset(Morwong4a,!is.na(age))
str(m4a.aged)
## extract length sample
m4a.length <- subset(Morwong4a,is.na(age))
str(m4a.length)
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