SpatialPosition (version 1.1)

rasterToContourPoly: Create a SpatialPolygonsDataFrame from a Raster

Description

This function creates a contour SpatialPolygonsDataFrame from a raster.

Usage

rasterToContourPoly(r, nclass = 8, breaks = NULL, mask = NULL)

Arguments

r

raster; the raster must contain only positive values.

nclass

numeric; a number of class.

breaks

numeric; a vector of break values.

mask

SpatialPolygonsDataFrame; mask used to clip contour shapes. The mask should have a smaller extent than r.

Value

• The ouput of the function is a SpatialPolygonsDataFrame. The data frame of the outputed SpatialPolygonsDataFrame contains four fields: id (id of each polygon), min and max (minimum and maximum breaks of the polygon), center (central values of classes)

Details

This function uses the rgeos package.

See Also

stewart, rasterStewart, plotStewart, quickStewart, CreateGrid, CreateDistMatrix.

Examples

data("spatData")
mystewart <- stewart(knownpts = spatPts, varname = "Capacite",
                     typefct = "exponential", span = 1000, beta = 3,
                     resolution = 50, longlat = FALSE,
                     mask = spatMask)
# Create a raster of potentials values
mystewartraster <- rasterStewart(x = mystewart)
# Create contour SpatialLinesDataFrame
contourpoly <- rasterToContourPoly(r = mystewartraster,
                                   nclass = 6,
                                   mask = spatMask)
# Created breaks
bks <- unique(c(contourpoly$min, contourpoly$max))
# Display the map
library(cartography)
opar <- par(mar = c(0,0,1.2,0))
choroLayer(spdf = contourpoly,
           df = contourpoly@data,
           var = "center", legend.pos = "topleft",
           breaks = bks, border = "grey90",
           lwd = 0.2,
           legend.title.txt = "Potential number\nof beds in the\nneighbourhood",
           legend.values.rnd = 0)
plot(spatMask, add = TRUE)
propSymbolsLayer(spdf = spatPts, df = spatPts@data, var = "Capacite",
                 legend.title.txt = "Number of beds",
                 col = "#ff000020")
layoutLayer(title = "Global Accessibility to Public Hospitals",
            south = TRUE, sources = "", author = "")
par(opar)