Note that the array returned may not be exactly the same as the effort
argument that was passed in to project(). This is because only the saved
effort is stored (the frequency of saving is determined by the argument
t_save).
Examples
str(getEffort(NS_sim))
#> num [1:44, 1:12] 0 0 0 0 0 0 0 0 0 0 ...
#> - attr(*, "dimnames")=List of 2
#> ..$ time: chr [1:44] "1967" "1968" "1969" "1970" ...
#> ..$ gear: chr [1:12] "Sprat" "Sandeel" "N.pout" "Herring" ...
