data frame containing at least a column giving the the time (and date) of the
measurements ordered by sample and chronologically. A column containing the sample IDs is optionally required if several samples
were measured.
sample
optional name of the column in data containing the sample
IDs, default: "sample".
date.and.time
optional name of the column in data containing the time (and date) as class POSIXct,
default: "date.and.time"
Value
The original data frame extended by a numerical vector containing time since start
(min) of the measurements.