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.dfA data frame with 10 observations on the following 2 variables.
Yeara numeric vector indicating the year of collection (a fractional number)
Sodium.ppma numeric vector of sodium concentrations (ppm)