read.cm {oce} | R Documentation |
Read a current-meter data file, producing an object of type
cm
.
read.cm(file, from=1, to, by=1, tz=getOption("oceTz"), type=c("s4"), longitude=NA, latitude=NA, debug=getOption("oceDebug"), monitor=FALSE, processingLog, ...)
file |
a connection or a character string giving the name of the file to load. |
from |
index number of the first measurement to be read, or the time of
that measurement, as created with |
to |
indication of the last measurement to read, in a format matching
that of |
by |
an indication of the stride length to use while walking through the
file. If this is an integer, then |
longitude |
optional signed number indicating the longitude in degrees East. |
latitude |
optional signed number indicating the latitude in degrees North. |
type |
character string indicating type of file (ignored at present). |
tz |
character string indicating time zone to be assumed in the data. |
debug |
a flag that turns on debugging. The value indicates the depth within the call stack to which debugging applies. |
monitor |
ignored at present. |
processingLog |
if provided, the action item to be stored in the log. This parameter is typically only provided for internal calls; the default that it provides is better for normal calls by a user. |
... |
optional arguments passed to plotting functions. |
There is function has been tested on only a single file, and the data-scanning algorithm was based on visual inspection of that file. Whether it will work generally is an open question. It should be noted that the sample file had several odd characteristics, some of which are listed below.
The file contained two columns named "Cond"
, which was guessed
to stand for conductivity. Since only the first contained data, the second was
ignored, but this may not be the case for all files.
The unit for "Cond"
was stated in the file to be "mS"
,
which makes no sense, so the unit was assumed to be mS/cm, and the value was
divided by the standard value 42.914mS/cm (see Culkin and Smith, 1980),
to estimate the conductivity ratio.
The file contained a column named "T-Temp"
, which is not
something the author has seen in his career. It was assumed to stand for
in-situ temperature.
The file contained a column named "Depth"
, which is not something
an instrument can measure. Presumably it was calculated from pressure (with
what atmospheric offset, though?) and so pressure was inferred from it using
swPressure
.
The file contained several columns that lacked names. These were ignored.
The file contained several columns that seem to be derived from the
actual measured data, such as "Speed"
, "Dir"
, "N-S Dist"
,
etc. These are ignored.
The file contained several columns that were basically a mystery to the
author, e.g. "Hx"
, "Hy"
, "Vref"
, etc. These were ignored.
Based on such considerations, read.cm.s4()
reads only the columns that
were reasonably well-understood based on the sample file. Users who need more
columns should contact the author.
An object of class
"cm"
, which contains
measurements made with a current-meter device. The data
slot will
contain time
, u
(eastward velocity, converted from cm/s to m/s),
v
(northward velocity, converted from cm/s to m/s) salinity
(salinity, with the caution that the values in the sample file seem about 6PSU
higher than they should be), temperature
(temperature, assumed
in-situ), and pressure
(pressure, calculated with
swPressure
based on the "Depth"
column in the file).
Caution.
The value in the "Hdg"
file is stored as heading
in the data, but this is just a guess.
See “Details” for an explanation of why other columns are ignored.
Dan Kelley
Culkin, F., and Norman D. Smith, 1980. Determination of the concentration of potassium chloride solution having the same electrical conductivity, at 15 C and infinite frequency, as standard seawater of salinity 35.0000 ppt (Chlorinity 19.37394 ppt). IEEE Journal of Oceanic Engineering, 5, pp 22-23.
The documentation for cm-class
explains the structure of
cm
objects, and also outlines the other functions dealing with them.
## Not run: library(oce) cm <- read.oce("cm_interocean_0811786.s4a.tab") summary(cm) plot(cm) ## End(Not run)