seabed_area: Calculate planimetric seabed area
In lucymerobinson/CCAMLRGIS: bridging R and the CCAMLR online GIS

Calculate planimetric seabed area within the single depth class and/or multiple depth classes

1	seabed_area(bathymetry, Polys, fishable_area, depth_classes = NA)

`bathymetry`	is data in a raster file format upon which the calculation is based, it is assumed that all bathymetry values above zero have been removed.
`Polys`	is the polygon(s) region of interest in the SpatialPolygonsDataFrame
`fishable_area`	is TRUE if the planimetric seabed area in the fishable depth range (i.e. 800-1600m) will be calculated if FALSE then the total seabed area will be calculated
`depth_classes`	is a character vector that includes the minimum and maximum depth within each depth class e.g. c("0-600","600-1800","1800-max")