webtide {oce} | R Documentation |
Get a tidal prediction from a WebTide database
webtide(action=c("map", "predict"), longitude, latitude, node, time, basedir=getOption("webtide"), region="nwatl", plot=TRUE, tformat, debug=getOption("oceDebug"), ...)
action |
An indication of the action, either |
longitude |
longitude at which prediction is required (ignored if |
latitude |
latitude at which prediction is required (ignored if |
node |
node to look up; only needed if |
time |
times at which prediction is to be made. If not supplied, this will be the week starting at the present time, incrementing by 15 minutes. |
basedir |
directory containing the |
region |
database region, given as a directory name in the WebTide directory. For example,
|
plot |
boolean indicating whether to plot. |
tformat |
optional argument passed to |
debug |
a debugging flag; set higher for more debugging and 0 for no debugging |
... |
optional arguments passed to plotting functions. A common
example is to set |
If action="map"
then a map is drawn, with a dot for the lower-left corner of each
triangle used in the finite-element tidal simulation upon which WebTide predictions are based. If
node
is missing, then locator
is called, so that the user can indicate a spot
of interest on the map, and this point is indicated on the map (and in the return value). If
node
is provided, however, the point is indicated but locator
is not called.
(This second style is of use in documenting interactive work after the fact.)
If action="predict"
then either a node number or the longitude and latitude
must be specified. If plot=TRUE
(the default) then a plot is drawn, but no plot is
produced otherwise. In either case, the (silent) return value is a list as described in the next
section. The times used for prediction are specified with the time
argument, and if this
is not specified then a week following the present time is used.
Naturally, webtide
will not work unless WebTide has been installed on the computer.
If action="map"
and plot=TRUE
, the return value is a list containing the index
of the nearest node, along with the latitude
and longitude
of that node. If
action="map"
and plot=FALSE
, the return value is a list of all nodes, longitude,
and latitudes.
If action="predict"
, the return value is a list containing a vector of times (time
),
as well as vectors of the predicted elevation
in metres and the predicted horizontal
components of velocity, u
and v
, along with the node
number, and the
basedir
and region
as supplied to this function.
Dan Kelley
The WebTide software may be downloaded for free at
the Department of Fisheries and Oceans (Canada) website, which in February
2016 was http://www.bio.gc.ca/science/research-recherche/ocean/webtide/index-en.php
,
although this site seems not to be particularly static.
Note that WebTide is not an open-source
application, as it consists mainly of compiled Java code, which precludes examination of the
source. The present function relies on a certain structure of the WebTide data files, and since
the WebTide source is closed, this was done partly by guessing. This means that the present
function is brittle to changes in WebTide; users should be on the lookout for odd results.
## Not run: library(oce) prediction <- webtide("predict", longitude=-69.61, latitude=48.14) ## End(Not run)