One of forward and reverse. The default is forward meaning the differences
are calculated
in such a way that the difference
between the current value and the next is returned
exclude
A character vector specifying what classes should be removed. See examples below
na.rm
Logical. Should missing values be removed? The missing values referred to are those introduced during the calculation ie when subtracting a row with itself.
Defaults to FALSE.
na_action
If na.rm is TRUE, how should missing values be replaced? Depending on the
value as set out in `na_replace`, the value can be replaced as per the user's requirement.