metadata, data and processingLog.ctd. Accessing column values.
Column data may be accessed as e.g. ctd[["salinity"]],
ctd[["temperature"]], ctd[["pressure"]], etc. There may be
other columns also, depending on the CTD configuration.
Depth is accessed with e.g. ctd[["depth"]], while its negative, the
vertical coordinate, is accessed with e.g. ctd[["z"]]; note that
these are calculated using swDepth and swZ, and
that any values that may have been read in a data file are ignored.
Potential temperature is calculated with ctd[["potential
temperature"]]. The TEOS-10 defined quantity called ``absolute
salinity'' is retrieved with ctd[["absolute salinity"]],
ctd[["absoluteSalinity"]], or ctd[["SA"]], while
``conservative temperature'' is retrieved with ctd[["conservative
temperature"]], ctd[["conservativeTemperature"]], or
ctd[["CT"]]. (None of the TEOS-10 quantities are stored in the
data; rather, they are computed if requested.)
Accessing scalar values.
Various scalar quantities are also available, e.g.
ctd[["longitude"]], etc.
Accessing derived values.
The square of buoyancy frequency $N$ is retrieved with
ctd[["N2"]] or swN2, density ratio with
ctd[["Rrho"]] and spiciness with ctd[["spice"]].
Assigning values.
Items stored in the object may be altered with e.g.
ctd[["salinity"]] <- rep(35,10). Note that this method will not
work with derived quantities such as conservative temperature, etc.
Overview of contents.
The show method (e.g. show(ctd)) displays information about
the object.
read.ctd, and a CTD object can also be created with
as.ctd. See read.ctd for references on data
formats used in CTD files.
Statistical summaries are provided by summary.ctd, while
show displays an overview.
CTD objects may be plotted with plot.ctd, which does much of
its work by calling plotProfile or plotTS, both
of which can also be called by the user, to get fine control over the plots. A CTD profile can be isolated from a larger record with
ctdTrim, a task made easier when plotScan is used
to examine the results. Towyow data can be split up into sets of profiles
(ascending or descending) with ctdFindProfiles. CTD data may
be smoothed and/or cast onto specified pressure levels with
ctdDecimate.
Low-level manipulation may be done with functions such as
ctdAddColumn and ctdUpdateHeader. Additionally,
many of the contents of CTD objects may be altered with the [[]]
scheme discussed above, and skilled uses may also manipulate the contents
directly.