map arbitrary metavariables as extra arguments for FUN

[qgeissmann]

When loading data, and using FUN, sometimes we want to adapt the behaviour of the function FUN according to metavariables.

[qgeissmann]

Testing the proposed feature:

dir <- paste0(scopr_example_dir(), "/ethoscope_results/")
metadata <- data.table(machine_name = c("E_014", "E_014","E_029"),
                       date = c("2016-01-25", "2016-02-17","2016-01-25"),
                       time = c("21:46:14", NA, NA),
                       test=c(1,2,3)
                       )

metadata

foo <- function(data, movement_threshold=0.1){
  print(movement_threshold)
  return(data)
}


query <- link_ethoscope_metadata(metadata,dir)
print(query)

Wo for instance, we want to call the function foo on the data, but for each individual, use the metavariable "test" (look it is in the metadata) as the (dummy) movement threshold (movement_threshold):

dt <- load_ethoscope(query,
                      verbose=F,
                      FUN=foo,
                      map_arg=list( movement_threshold = "test"))

[pepelisu]

This would be an awesome feature to have.

[qgeissmann]

it is basically there @pepelisu (ac61b7f). Untested though, would be nice to have some feed back, write tests and add to the next release...

[antortjim]

I confirm it works 👍
In the same line, I think providing the ZT0 time (reference_hour) in the metadata should be possible too.
This is especially convenient if one is providing flies with different timezones in the same metadata i.e. the same call to load_ethoscope. That way, the same call to load_ethoscope can use different ZT0

It can be done by placing this snippet before creating the arg_list in the parse_wrapper, assuming the column in the metadata is called foo. I guess foo should be reference_hour.

if(is.null(reference_hour) & "foo" %in% colnames(row))
  reference_hour <- row[, foo]

[antortjim]

Or maybe even more simple, using your map_arg implementation:

• Place this line before defining load_fun
map_arg <- c(map_arg, reference_hour = "foo")
• and remove reference_hour from the arg_list (it will be added via arg_val), to avoid having the argument passed twice.