GRTS.access: Perform a GRTS sampling on a access database table via ODBC
In ThierryO/grts: Spatially Balanced Sampling Based on GRTS

Perform a GRTS sampling on a access database table via ODBC

1 2	GRTS.access(channel, tablename, grts.vars, cellsize, samplesize, availableLevels = 20, reset = FALSE, prefix = "L", prob)

`channel`	an ODBC channel to the database
`tablename`	the name of the table in the database
`grts.vars`	the name of the variabeles which define the GRTS sampling space. Typically an X and Y variable. However the only limitations are that all variables are numeric and the number of variables must be at least one.
`cellsize`	the size of the smallest GRTS cell for each dimension.
`samplesize`	the required sample size
`availableLevels`	the number of available GRTS levels in the database. These must be named L01, L02, ... Currently available levels is limited to 99
`reset`	logical value. If FALSE the current GRTS randomisation is completed. If TRUE a new GRTS randomisation will start.
`prefix`	Prefix of the fields that store the randomisation
`prob`	The name of the fields with the sampling probability