metadata, data and processingLog.ctd. Accessing values. Data may be accessed as e.g.
ctd[["salinity"]], where the string could also be e.g.
"temperature" or "pressure" for column data, or
"latitude" or "longitude" for scalars. (The names of the
columns are displayed with show(). The name of the source file is
found with "filename".
The TEOS-10 defined quantities called ``absolute salinity'' and
``conservative temperature'' can be retrieved with
ctd[["absoluteSalinity"]] (or ctd[["SA"]]) and
ctd[["conservativeTemperature"]] (or ctd[["CT"]]),
respectively. Note that these are not saved in the data object, but
are calculated as needed.
Another important derived quantity is buoyancy frequency $N$, and
e.g. ctd[["N2"]] calls swN2 to compute its square.
Assigning values. Items stored in the object may be altered with
e.g. ctd[["salinity"]] <- rep(35,10). Note that this does not
apply to 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.
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. The editing of CTD objects (e.g. to isolate downcasts) can be done with
ctdTrim, a task made easier when plotScan is
used to examine the results. CTD data may be smoothed and/or cast onto
specified pressure levels with ctdDecimate.
In addition to the direct accessors discussed above, low-level manipulation
may be done with ctdAddColumn and
ctdUpdateHeader. The contents of CTD objects may be altered
with the [[]] scheme discussed in the previous section, and skilled
uses may also manipulate the contents directly.