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\name{mapasp}
\alias{mapasp}
\alias{degreeLabelsEW}
\alias{degreeLabelsNS}
\title{ Calculate aspect ratio for plotting geographic maps;
create nice degree axis labels }
\description{ Calculate aspect ratio for plotting geographic maps;
create nice degree axis labels }
\usage{
mapasp(data, xlim, ylim)
degreeLabelsEW(x)
degreeLabelsNS(x)
}
\arguments{
\item{data}{ object of class or extending \code{Spatial}}
\item{xlim}{ the xlim argument passed (or derived from bounding box) }
\item{ylim}{ the ylim argument passed (or derived from bounding box) }
\item{x}{ numeric; values at which tics and marks will be generated }
}
\value{
\code{mapasp} is used for the aspect argument in lattice plots and spplot;
let x = dy/dx, with dy and dx the y- and x-size of the map.
let s = 1/cos((My * pi)/180) with My the y coordinate of the middle of the map
(the mean of ylim)
for latlong (longlat) data, \code{mapasp} returns s * x.
for other data, mapasp returns "iso".
}
\note{the values for \code{x} are typically obtained from \link{axTicks}}
\seealso{ \link[lattice]{levelplot} in package \code{lattice}}
\keyword{dplot}
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