McSpatial (version 1.1.1)

mappoints: Maps showing points on a shape file

Description

Uses the classInt package to show a color ramp of points placed on a shape file map

Usage

mappoints(shpfile,longvar,latvar,pointvar,sampvar=NULL,nclass=8,
  col="RdBu",pointsize=.6,colreverse=TRUE,xlimfact=c(1,1),ylimfact=c(1,1),
  legendloc=NULL,legendsize=.75,legenddigits=4,title=NULL)

Arguments

shpfile

The shape file, a polygon map showing areas.

longvar

Longitude variable for the point data, in degrees.

latvar

Latitude variable for the point data, in degrees.

pointvar

The variable to be mapped.

sampvar

A variable indiciating which observations to include in the map. Tracts for which sampvar=F will not be drawn.

nclass

The number of classes used when mapping pointvar. Default: nclass=8.

col

Color scheme for the map. All of RColorBrewer's schemes are available, e.g., "Blues", "BuGn", "BuPu", and "GnBu". Default: "RdBu"

pointsize

The size of the points drawn on the map. Fed directly to the cex option for the points command. Default: pointsize=.6.

colreverse

If TRUE, reverses the order of the color ramp for the col options. Default: colreverse=T.

xlimfact

A vector of factors used to adjust the limits for the box around the map. The limits for the x-axis (i.e., the longitudes) are xlim=c(min(longvar),max(longvar))*xlimfact. Since the geographic coordinates are expressed in degrees, small adjustments wil

ylimfact

The counterpart to xlimfact for the y (i.e., latitude) axis. Default: ylimfact = c(1,1).

legendloc

The location for the legend, e.g., "topleft" or "bottom". By default, the legend is omitted.

legendsize

The font size for the legend. Fed directly to the cex option for the legend command. Default: legendsize=.75.

legenddigits

Number of significant digits for the numbers shown in the legend. Default: legenddigits = 4.

title

A title for the map.

See Also

mapoverlay mapplot

Examples

library(maptools)
cmap <- readShapePoly(system.file("maps/CookCensusTracts.shp",
  package="McSpatial"))
carea <- cmap$CAREA=="Albany Park"|cmap$CAREA=="Edgewater"|
  cmap$CAREA=="Edison Park"|cmap$CAREA=="Forest Glen"|
  cmap$CAREA=="Jefferson Park"|cmap$CAREA=="Lincoln Square"|
  cmap$CAREA=="North Park"|cmap$CAREA=="Norwood Park"|
  cmap$CAREA=="Rogers Park"|cmap$CAREA=="Uptown"|
  cmap$CAREA=="West Ridge"
carea[is.na(carea)] <- FALSE

data(matchdata)
mappoints(cmap,matchdata$longitude,matchdata$latitude,matchdata$lnprice,
  sampvar=carea,legendloc="bottomleft",title="Location of Home Sales")