Sodium concentrations (ppm) collected over several years. The sample dates are recorded as the year of collection (2-digit format) plus a fractional part indicating when during the year the sample was collected.
EPA.09.Ex.17.7.sodium.df
A data frame with 10 observations on the following 2 variables.
Year
a numeric vector indicating the year of collection (a fractional number)
Sodium.ppm
a numeric vector of sodium concentrations (ppm)