read.ctd.odf: Read a ctd File in odf Format

Description

Read a ctd File in odf Format

Usage

read.ctd.odf(
  file,
  columns = NULL,
  station = NULL,
  missingValue,
  deploymentType = "unknown",
  monitor = FALSE,
  exclude = NULL,
  encoding = "latin1",
  debug = getOption("oceDebug"),
  processingLog,
  ...
)

Value

This function returns a ctd object.

Arguments

file

either a connection or a character value naming a file. For read.ctd.sbe() and read.ctd.woce(), this may be a wildcard (e.g. "*.cnv" or "*.csv") in which case the return value is a vector containing CTD objects created by reading the files from list.files() with pattern set to the specified wildcard pattern.

columns

an optional list that can be used to convert unrecognized data names to resultant variable names. This is used only by read.ctd.sbe() and read.ctd.odf(). For example, if a data file named salinity as "SAL", then using

d <- read.ctd(f, columns=list(
    salinity=list(name="SAL",
                  unit=list(unit=expression(),
                  scale="PSS-78"))))

would assign the "SAL" column to the salinity entry in the data slot of the CTD object returned by the read.* function.

station

optional character string containing an identifying name or number for the station. This can be useful if the routine cannot determine the name automatically, or if another name is preferred.

missingValue

optional missing-value flag; data matching this value will be set to NA upon reading. If this is provided, then it overrules any missing-value flag found in the data. For Seabird (.cnv) files, there is usually no need to set missingValue, because it can be inferred from the header (typically as -9.990e-29). Set missingValue=NULL to turn off missing-value detection, even in .cnv files that contain missing-value codes in their headers. If missingValue is not specified, then an attempt is made to infer such a value from the data, by testing whether salinity and/or temperature has a minimum that is under -8 in value; this should catch common values in files, without false positives. A warning will be issued in this case, and a note inserted in the processing log of the return value.

deploymentType

character string indicating the type of deployment. Use "unknown" if this is not known, "profile" for a profile (in which the data were acquired during a downcast, while the device was lowered into the water column, perhaps also including an upcast; "moored" if the device is installed on a fixed mooring, "thermosalinograph" (or "tsg") if the device is mounted on a moving vessel, to record near-surface properties, or "towyo" if the device is repeatedly lowered and raised.

monitor

boolean, set to TRUE to provide an indication of progress. This is useful if filename is a wildcard.

exclude

either a character value holding a regular expression that is used with grep() to remove lines from the header before processing, or NULL (the default), meaning not to exclude any such lines. The purpose of this argument is to solve problems with some files, which can have thousands of lines that indicate details that are may be of little value in processing. For example, some files have thousands of lines that would be excluded by using exclude="PROCESS='Nulled the .* value" in the function call.

encoding

a character value that indicates the encoding to be used for this data file, if it is textual. The default value for most functions is "latin1", which seems to be suitable for files containing text written in English and French.

debug

an integer specifying whether debugging information is to be printed during the processing. This is a general parameter that is used by many oce functions. Generally, setting debug=0 turns off the printing, while higher values suggest that more information be printed.

processingLog

if provided, the action item to be stored in the log. This is typically only provided for internal calls; the default that it provides is better for normal calls by a user.

...

additional arguments, passed to called routines.

Caution

Lacking detailed documentation of the ODF file format, the read.odf() and read.ctd.odf() functions were crafted based on inspection of data files, and so some guesses had to be made.

The PARAMETER_HEADER chunks describing quality-control flags are a case in point. These contain NAME components that refer to other PARAMETER_HEADER chunks that hold measured data. However, those references are not always matched well with the data names, and even if they do match, the cross-reference syntax used by the Bedford Institute of Oceanography differs from that used by l’Institut Maurice-Lamontagne. To simplify coding, it was assumed that each quality-control sequence applies to the data sequence immediately preceding it. (This assumption is made in other analysis systems.)

It is also prudent to pay attention to the units decoding, which read.odf() handles by calling unitFromString(). Be on the lookout for incorrect temperature scales, which are sometimes reported with nonstandard strings in ODF files. Also, note that you may see warnings about conductivity ratios, which some ODF files incorrectly suggest have dimensions.

Author

Dan Kelley

Details

read.ctd.odf reads files stored in Ocean Data Format, used in some Canadian hydrographic databases.

References

For sources that describe the ODF format, see the documentation for the odf class.