| ctd.trim {oce} | R Documentation |
Trim start/end portions of a CTD cast.
ctd.trim(x, method="downcast",parameters=NULL)
x |
A ctd object, e.g. as read by read.ctd. |
method |
Various methods exist, some of which use parameters:
selection <- trim.ctd(ctd, "index", seq(10,30))
selects data points 10, 11, ... 30.scan, time, etc.) falls
in the range of values indicated by parameters. If one
parameter is given, it is a lower limit. If two parameters
are given, they are a range.
For example, ctd2 <- trim.ctd(ctd, "scan", 5)
starts at scan number 5 and continues to the end,
while ctd3 <- trim.ctd(ctd, "scan", c(5,100))
also starts at scan 5, but extends only to scan 100. |
parameters |
Depends on method; see above. |
The code is quite straightforward, and indeed it's a good idea to check
the code, if you want something more sophisticated, e.g. selecting
data based on a T-S criterion. The most common use of this is to run
plot.ctd.scan() together with ctd.trim, identifying
by eye an initial period in which the CTD is in the air or
unequilibrated in the water, and a final period in which the CTD is
no longer descending.
A new ctd object.
Dan Kelley Dan.Kelley@Dal.Ca
The Seabird CTD instrument is described at http://www.seabird.com/products/spec_sheets/19plusdata.htm.
The ctd object may be read with read.ctd.
plot.ctd.scan is very useful in providing guidance
in how to trim; it is common practice to plot a scan first, then
to trim by scan.
library(oce) data(ctd) ctd.trimmed <- ctd.trim(ctd, "pressure", c(3, 5)) summary(ctd.trimmed)