read.cm {oce}R Documentation

Read a current-meter data file

Description

Read a current-meter data file, producing an object of type cm.

Usage

read.cm(file, from=1, to, by=1, tz=getOption("oceTz"),
        type=c("s4"),
        longitude=NA, latitude=NA,
        debug=getOption("oceDebug"), monitor=FALSE, processingLog, ...)

Arguments

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 as.POSIXct (hint: use tz="UTC").

to

indication of the last measurement to read, in a format matching that of from.

by

an indication of the stride length to use while walking through the file. If this is an integer, then by-1 measurements are skipped between each pair of profiles that is read. This may not make much sense, if the data are not equi-spaced in time. If by is a string representing a time interval, in colon-separated format, then this interval is divided by the sampling interval, to get the stride length. BUG: if the data are not equi-spaced, then odd results will occur.

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.

Details

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.

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.

Value

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.

Author(s)

Dan Kelley

References

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.

See Also

The documentation for cm-class explains the structure of cm objects, and also outlines the other functions dealing with them.

Examples

  ## Not run: 
    library(oce)
    cm <- read.oce("cm_interocean_0811786.s4a.tab")
    summary(cm)
    plot(cm)
  
## End(Not run)

[Package oce version 0.9-18 Index]