webtide | R Documentation |
Get a tidal prediction from a WebTide database. This only works if the standalone WebTide application is installed, and if it is installed in a standard location. The details of installation are not within the oce purview.
webtide(
action = c("map", "predict"),
longitude,
latitude,
node,
time,
basedir = getOption("webtide"),
region = "nwatl",
plot = TRUE,
tformat,
pch = 20,
cex = 0.5,
nodecol = "black",
landcol = rgb(0.82, 0.71, 0.55, 0.5),
debug = getOption("oceDebug"),
...
)
action |
An indication of the action, either |
longitude , latitude |
optional location at which prediction is required
(ignored if |
node |
optional integer relating to a node in the database. If |
time |
a vector of times (in the UTC timezone) at which prediction is to
be made. If not supplied, this will be the week starting at the present time,
computed with |
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 |
pch |
integer giving the character code (default is 20, for a bullet), used if a map-style plot is requested. |
cex |
numeric giving the character expansion factor (default is 0.5), used if a map-style plot is requested. |
nodecol |
colour to be used for dots on a map-style plot. |
landcol |
colour of land, used in plotting maps. The default is a
semi-transparent tan colour. Set to |
debug |
an integer specifying whether debugging information is
to be printed during the processing. This is a general parameter that
is used by many |
... |
optional arguments passed to plotting functions. A common
example is to set |
There are two methods of using this function. Case 1: action="map"
. In
this case, if plot
is FALSE
, a data frame is returned, containing all the
node
s in the selected database, along with all the latitude
s and
longitude
s. This value is also returned (silently) if plot
is true, but
in that case, a plot is drawn to indicate the node locations. If latitude
and longitude
are given, then the node nearest that spot is indicated on
the map; otherwise, if node
is given, then the location of that node is
indicated. There is also a special case: if node
is negative and
interactive()
is TRUE
, then locator()
is called, and the node nearest
the spot where the user clicks the mouse is indicated in the plot and in the
return value.
Case 2: action="predict"
. If plot
is FALSE
, then a list is returned,
indicating time
, predicted elevation
, velocity components u
and v
,
node
number, the name of the basedir
, and the region
. If plot
is
TRUE
, this list is returned silently, and either a map or a set of three
time-series plots (for u, v and water level) is plotted. (In the
second case, users may wish to call par(mfrow=c(3,1))
first.)
The value depends on action
:
If action="map"
the return value is an indication of the location
of a selected node, or (if node
is NULL) of all nodes.
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. If plot
is FALSE
,
this value is returned invisibly.
WebTide is not an open-source application, so the present function was designed based on little more than guesses about the WebTide file structure. Users should be on the lookout for odd results.
# needs WebTide at the system level library(oce) # 1. prediction at Halifax NS longitude <- -63.57 latitude <- 44.65 prediction <- webtide("predict", longitude=longitude, latitude=latitude) mtext(paste0("prediction at ", latitude, "N and ", longitude, "E"), line=0.75, side=3) # 2. map webtide(lon=-63.57,lat=44.65,xlim=c(-64,-63),ylim=c(43.0,46))
Dan Kelley
The WebTide software may be downloaded for free at the
Department of Fisheries and Oceans (Canada) website at
http://www.bio.gc.ca/science/research-recherche/ocean/webtide/index-en.php
(checked February 2016 and May 2017).
Other things related to tides:
[[,tidem-method
,
[[<-,tidem-method
,
as.tidem()
,
plot,tidem-method
,
predict.tidem()
,
summary,tidem-method
,
tidalCurrent
,
tidedata
,
tidem
,
tidem-class
,
tidemAstron()
,
tidemVuf()
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