Create problem formulation, feature requires raster

[ricschuster]

It seems to me that both the 'standard'

problem(x, features, ...)

function as well as the marxan_problem function require the features to be supplied as rasters.

The initial idea for the marxan_problem function was this:

p <-marxan_problem(pu_polygons, cost=..., features=..., locked_in=..., 
  locked_out=..., penalty=..., edge_factor=....)

where the dots are column names or vectors of values.

I think it would be great to allow for the latter case.

Along the same lines, I think it would also be good if in the standard 'problem' function we would allow to mix spatialdataframe classes with dataframes (as features). That's the way I often use shapfefiles and csv files together. Not sure how common it is, but I would imagine its fairly common.

@jeffreyhanson, how is your availability in the next little while? Do you still have time to tackle these things or do you need to focus on finishing your PhD?

[jeffreyhanson]

Yeah, I didn't get around to doing that.

To implement this, we could add the following method to problem:

p <- problem(cost, features, cost_name)

where cost is a SpatialPolygonsDataFrame class, cost_name is a character specifying the column name with cost, and features is a character vector specifying the column names with the feature abundances. So that users can specify the problem data using just a SpatialPolygonsDataFrame.

We would probably have to switch problem to S4 though, since S3 won't allow dispatch on multiple arguments.

After adding this functionality, it would be pretty straight forward to add a new method to the marxan_problem that does what you want.

I don't really have the time at the moment to work on this. I might be able to find some spare time in the next few weeks, but I can't make any promises.

[ricschuster]

Thanks Jeff. I can try to work this out. Will be good practice for me anyways.
In case you do get a chance to look at this, please let me know so we don't overlap in our efforts.