R help - Sep 2012 - Panels of Geographical Maps

Dear All,
Please consider the snippet at the end of the email.
My problem is rather simple: I can generate individual maps of a country  
where each region is colored according to a scalar, but I am experiencing  
problems when I try to combine e.g. 2 maps into a single figure using the  
mfrow(2,1) parameter.
This does not give me any trouble when I use "plot", but I must be  
misunderstanding something when I resort to "spplot" (one plot gets  
overwritten and no panel is generated).
Any suggestion is really appreciated.
Cheers

Lorenzo

#########################################################################################

library(sp)
con <- load("ITA_adm1.RData")
unemployment <- c(6.2,11.2,9.5,11.2,11.2,2.9,
        3.4,6.4,4.8,3.4,4.2,8.1,4.2,9.9,13.0,4.3,2.7,4.6,3.2,3.3)
gadm$unemployment <- as.factor(unemployment)
col = rev(heat.colors(length(levels(gadm$unemployment))))
par.set <- list(axis.line=list(col="transparent"),
                 clip=list(panel="off"),
                 par.main.text=list(col="white"),
                 axis.text=list(col="white"), fontsize=list(text=18))
png("unemployment2.png", width=630, height=630, bg="grey15")
print(spplot(gadm, "unemployment", col.regions=col,
col="grey15",
        main=list(label="Italia - Tassi di disoccupazione 2007"),
        res=88, par.settings=par.set))
dev.off()



png("unemployment-panel.png", width=630, height=630,
bg="grey15")
par(mfrow=c(2,1), mar = c(4.5,5, 1, 1) + 0.1)
print(spplot(gadm, "unemployment", col.regions=col,
col="grey15",
        main=list(label="Italia - Tassi di disoccupazione 2007"),
        res=88, par.settings=par.set))
print(spplot(  gadm, "unemployment", col.regions=col,
col="grey15",
        main=list(label="Italia - Figure 2"),
        res=88, par.settings=par.set))

dev.off()

It turns out that there is already a solution

http://bit.ly/NmZg3S

Cheers

Lorenzo

------- Forwarded message -------
From: "Lorenzo Isella" <lorenzo.isella at gmail.com>
To: "r-help at stat.math.ethz.ch" <r-help at stat.math.ethz.ch>
Cc:
Subject: Panels of Geographical Maps
Date: Tue, 11 Sep 2012 22:58:43 +0200

Dear All,
Please consider the snippet at the end of the email.
My problem is rather simple: I can generate individual maps of a country
where each region is colored according to a scalar, but I am experiencing
problems when I try to combine e.g. 2 maps into a single figure using the
mfrow(2,1) parameter.
This does not give me any trouble when I use "plot", but I must be
misunderstanding something when I resort to "spplot" (one plot gets
overwritten and no panel is generated).
Any suggestion is really appreciated.
Cheers

Lorenzo

#########################################################################################

library(sp)
con <- load("ITA_adm1.RData")
unemployment <- c(6.2,11.2,9.5,11.2,11.2,2.9,
          3.4,6.4,4.8,3.4,4.2,8.1,4.2,9.9,13.0,4.3,2.7,4.6,3.2,3.3)
gadm$unemployment <- as.factor(unemployment)
col = rev(heat.colors(length(levels(gadm$unemployment))))
par.set <- list(axis.line=list(col="transparent"),
                   clip=list(panel="off"),
                   par.main.text=list(col="white"),
                   axis.text=list(col="white"),
fontsize=list(text=18))
png("unemployment2.png", width=630, height=630, bg="grey15")
print(spplot(gadm, "unemployment", col.regions=col,
col="grey15",
          main=list(label="Italia - Tassi di disoccupazione 2007"),
          res=88, par.settings=par.set))
dev.off()



png("unemployment-panel.png", width=630, height=630,
bg="grey15")
par(mfrow=c(2,1), mar = c(4.5,5, 1, 1) + 0.1)
print(spplot(gadm, "unemployment", col.regions=col,
col="grey15",
          main=list(label="Italia - Tassi di disoccupazione 2007"),
          res=88, par.settings=par.set))
print(spplot(  gadm, "unemployment", col.regions=col,
col="grey15",
          main=list(label="Italia - Figure 2"),
          res=88, par.settings=par.set))

dev.off()