[[ method works for all
oce objects, i.e.
objects inheriting from
oce-class. The purpose,
as with the related replacement method,
is to insulate users from the internal details of
objects, by looking for items within the various storage
slots of the object. Items not actually stored can also be
extracted, including derived data, units of measurement,
and data-quality flags.
The method uses a two-step process to try to find the
requested information. First, a class-specific function
is used to try to access the requested information (see
“Details of the specialized ... method”).
Second, if no match is found, a general function is used
(see ‘Details of the general method’). If neither
method can locates the requested item,
NULL is returned.
## S4 method for signature 'g1sst' x[[i, j, ...]]
Character string indicating the name of item to extract.
Optional additional information on the
Optional additional information (ignored).
If the specialized method produces no matches, the following generalized
method is applied. As with the specialized method, the procedure hinges
first on the value of
First, a check is made as to whether
i names one of the standard
oce slots, and returns the slot contents if so. Thus,
x[["metadata"]] will retrieve the
i is a string ending in the
"Unit", then the characters preceding that string
are taken to be the name of an item in the data object, and a list
containing the unit is returned. This list consists of an item
unit, which is an
an item named
scale, which is a string describing the
measurement scale. If the string ends in
" unit", e.g.
x[["temperature unit"]], then just the expression is returned,
and if it ends in
" scale", then just the scale is returned.
i is a string ending in
"Flag", then the corresponding
data-quality flag is returned (or
NULL if there is no such flag).
x[["salinityFlag"]] returns a vector of salinity
x is a ctd object.
If none of the preceding conditions are met, a check is done
to see if the
metadata slot contains an item with
the provided name, and that is returned, if so. A direct match
is required for this condition.
data slot is checked to see if it contains
an item with the name indicated by
i. In this case, a partial
match will work; this is accomplished by using
If none of the above-listed conditions holds, then
NULL is returned.
Other functions that extract parts of