WebPlot.RdWebPlot opens a new graphics device (currently based on
Cairo) and returns an object that can be used as a result of
FastRWeb functions or in web output.
WebPlot(width = 640, height = 480, type = "png", ...)width of the resulting plot (normally in pixels)
height of the resulting plot (normally in pixels)
type of the output
furhter arguments to be passed to Cairo
WebPlot generates a temporary file name that is accessible using
the "tmpfile" command of WebResult and opens a
new Cairo device with the specified parameteres. It
returns a WebPlot object that can be either retured directly
from the run() function (and thus resulting in one image) or
used with the out() function to reference the image in
an HTML page (see examples below).
Note that as.WebResult coercion is used to finalize the
result when returned directly and it will close the device, so
dev.off() is optional and not needed in that case. Also
WebPlot reserves the right to close any or all other
active WebPlot devices - this ensures that dev.off() may
not be neeed at all even when using multiple WebPlots.
WebPlot object.
The structure of the WebPlot class is considered internal and
should not be created directly. Current attributes include
file (filename), type (output type), mime (MIME
type), width, height.
## example 1: single image
## if saved as "plot.png.R"
## it can be served as http://server/cgi-bin/R/plot.png
run <- function(n = 100, ...) {
n <- as.integer(n)
# create the WebPlto device
p <- WebPlot(800, 600)
# plot ...
plot(rnorm(n), rnorm(n), pch=19, col="#ff000080")
# return the WebPlot result
p
}
## example 2: page containing multiple images
## if saved as "plotex.html.R"
## it can be served as http://server/cgi-bin/R/plotex.html
run <- function(...) {
out("<h2>Simple example<h2>")
data(iris) ## ideally, you'll use data from the Rserve session
attach(iris)
p <- WebPlot(600, 600)
plot(Sepal.Length, Petal.Length, pch=19, col=Species)
out(p)
p <- WebPlot(350, 600)
barplot(table(Species), col=seq.int(levels(Species)))
out(p)
done()
}