lags: extend dplyr to multiple lags
In mattdelhey/mdutils: Utilities for dealing with data.

extend dplyr to multiple lags

1	lags(x, lags = 1L:2L, default = NA, order_by = NULL, ...)

`x`	a vector of values
`lags`	vector of lags to be computed
`default`	value used for non-existant rows. Defaults to `NA`.
`order_by`	override the default ordering to use another vector
`...`	Needed for compatibility with lag generic.
`reduce`	function to reduce results