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\name{lineLabel}
\alias{lineLabel}
\alias{sp.lineLabel}
\alias{label}
\alias{sp.lineLabel-methods}
\alias{label-methods}
\alias{sp.lineLabel,Lines-method}
\alias{sp.lineLabel,SpatialLines-method}
\alias{label,SpatialLines-method}
\title{
Line label placement with spplot and lattice.
}
\description{ The \code{lineLabel} function produces and draws text
grobs following the paths defined by a list of \code{Line}
objects. The \code{sp.lineLabel} methods use this function to work
easily with \code{spplot}.}
\usage{
lineLabel(line, label,
spar=.6, position = c('above', 'below'),
textloc = 'constantSlope',
col = add.text$col,
alpha = add.text$alpha,
cex = add.text$cex,
lineheight = add.text$lineheight,
font = add.text$font,
fontfamily = add.text$fontfamily,
fontface = add.text$fontface,
lty = add.line$lty,
lwd = add.line$lwd,
col.line = add.line$col,
identifier = 'lineLabel',
...)
sp.lineLabel(object, labels, byid=TRUE,...)
label(object, text, ...)
}
\arguments{
\item{line}{a \code{list} of \code{Lines}.}
\item{object}{A \code{Lines} or \code{SpatialLines} object.}
\item{label, labels, text}{a string or expression to be printed
following the path of \code{line}. The \code{names} of \code{labels}
should match the values of the \code{ID} slot of the lines to
label. If \code{labels} is missing, the \code{ID} slot is used
instead. The \code{label} method is a wrapper function to extract
the \code{ID} slots and create a suitable \code{character} object
with the correct \code{names} values.}
\item{byid}{If TRUE (default) only the longest line of each unique
\code{ID} value will be labelled.}
\item{textloc}{a character or a numeric. It may be 'constantSlope',
'minSlope' or 'maxDepth', or the numeric index of the location. If
it is a numeric, its length must coincide with the number of
\code{Lines}.}
\item{spar}{smoothing parameter. With values near zero, the label
will closely follow the line. Default value is .6. See smooth.spline for details.}
\item{position}{character string ('above' or 'below') to define where
the text must be placed.}
\item{col, alpha, cex, lineheight, font, fontfamily,
fontface}{graphical arguments for the text. See gpar for details.}
\item{lty, lwd, col.line}{graphical parameters for the line. See gpar for details.}
\item{identifier}{A character string to identify the grob to be created.}
\item{...}{other arguments}
}
\author{
Oscar Perpiñán Lamigueiro.
}
\details{
Part of the label location code is adapted from \code{\link[lattice]{panel.levelplot}}.
\code{\link[stats]{smooth.spline}} is used to resample the segment of the line where the label is placed.}
\seealso{
\code{\link[sp]{spplot}}
\code{\link{sp.pointLabel}}
\code{\link{pointLabel}}
\code{\link[lattice]{panel.levelplot}}
\code{\link[stats]{smooth.spline}}
}
\examples{
data(meuse.grid)
coordinates(meuse.grid) = ~x+y
proj4string(meuse.grid) <- CRS("+init=epsg:28992")
gridded(meuse.grid) = TRUE
data(meuse)
coordinates(meuse) = ~x+y
data(meuse.riv)
meuse.sl <- SpatialLines(list(Lines(list(Line(meuse.riv)), "1")))
library(RColorBrewer)
myCols <- adjustcolor(colorRampPalette(brewer.pal(n=9, 'Reds'))(100), .85)
labs <- label(meuse.sl, 'Meuse River')
## Maximum depth
sl1 <- list('sp.lineLabel', meuse.sl, label=labs,
position='below', textloc='maxDepth',
spar=.2,
col='darkblue', cex=1,
fontfamily='Palatino',
fontface=2)
spplot(meuse.grid["dist"],
col.regions=myCols,
sp.layout = sl1)
## Constant slope
sl2 <- modifyList(sl1, list(textloc = 'constantSlope')) ## Default
spplot(meuse.grid["dist"],
col.regions=myCols,
sp.layout = sl2)
## Location defined by its numeric index
sl3 <- modifyList(sl1, list(textloc = 140, position='above'))
spplot(meuse.grid["dist"],
col.regions=myCols,
sp.layout = sl3)
}
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