data frame containing at least a numeric column containing the measured weights (g), ordered chronologically by sample. 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 ID, default: "sample"
fresh.weight
optional name of the column in data containing the numeric fresh weight (g) values, default: "fresh.weight"
Value
the original data frame extended by a numeric column containing the absolute
differences in fresh weight (g) beween the measurements of a sample. The first value of each
sample is NA since weight differences are computed from row i and i-1.