SplitR: Use the HYSPLIT model from inside R

Create and add a grid of latitude and longitude points to a model object.

add_grid(model, lat = NULL, lon = NULL, range = c(5, 5),
  division = c(0.5, 0.5), start_day = NULL, start_hour = NULL,
  end_day = NULL, end_hour = NULL, duration = NULL, heights = NULL,
  samp_type = "avg", samp_interval = 24, name = NULL)

`model`	A splitr modeling object
`lat`	A latitude value in decimal degrees for the point of reference on the grid.
`lon`	A longitude value in decimal degrees for the point of reference on the grid.
`range`	The latitude and longitude range about the `grid_ref`.
`division`	The division distances across the latitude and longitude ranges.
`start_day`	The day that the grid will become active and measuring particle concentrations. This should take the form of a single-length vector for a day (`"YYYY-MM-DD"`).
`start_hour`	The associated hour for the `start_day` variable, taking the form of a single integer hour (from `0` to `23`).
`end_day`	The day that the grid will cease to be active and no longer measuring particle concentrations. This should take the form of a single-length vector for a day (`"YYYY-MM-DD"`).
`end_hour`	The associated hour for the `end_day` variable, taking the form of a single integer hour (from `0` to `23`).
`duration`	A length of time in hours that the grid will remain active from the start date-time.
`heights`	A vector of heights for which there will be horizontal sampling grids.
`samp_type`	The method of reporting for the sampling grid. The default is `avg` for reporting average concentrations at every sampling interval. Other options are `snapshot` and `max` for concentrations at the time of sampling and for maximum concentrations, respectively.
`samp_interval`	The sampling interval in units of hours.
`name`	An identifier for this set of grid parameters.