EDIT1: I am using windows Vista and R 2.12.1
I am plotting 84 maps with spplot from the maptools package. I am using two viewports, one to plot the map, and one to plot a trend over time. I have written a loop which goes through each subset of the data, plots the map with countries color coded according to their scores, and plots the trend in that score over iterations. The loop looks like this:
##Read in the shape file, it is 48mb
eu27 <- readShapeSpatial("C:/Users/Thomas/Documents/EU27_shapefile/eu27_cyp.shp",proj4string=CRS ("+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs"))
##Drop not used variables from the shapefile data table
eu27@data <- data.frame(Order = 1:dim(eu27)[1], Country = as.character(eu27@data[,c("NAME_ISO")]))
##Fix longitude and lattitude for plotting later
xl <- c(-15,36)
yl <- c(33,73)
##Set the directory for storing the plots
setwd("C:/Users/Thomas/Documents/maps/")
##Define the breaks and colors
brks <- seq(0,8,1)
colcode <- terrain.colors(length(brks))
##Count used in the loop to keep track of iterations
count <- 1
##Vector to store the trend in time
total <- vector()
##Beginning of loop
for(i in 2001:2003){
for(j in 1:12){
##Subset the data and merge it with the shape file data table
dat <- d3[d3$Year == i & d3$Month == j, c("No","No.Neg","Country")]
eu27dat <- merge(eu27@data,dat, by="Country", all.x=TRUE)
eu27@data <- eu27dat[order(eu27dat$Order),]
eu27@data$tot <- eu27@data$No + eu27@data$No.Neg
##Store the map plot with countries color coded in the plot1 object
plot1 <- spplot(eu27, "tot", main = paste("Year: ",i,", Month: ",j, sep = ""), xlim=xl, ylim=yl, at = brks, col.regions = colcode)
##Remove the variables created
eu27@data$No <- NULL
eu27@data$No.Neg <- NULL
eu27@data$tot <- NULL
##Update the vector with trend data from the current iteration
total[count] <- sum(dat$No.Neg, na.rm = T)
##Store the trend data plot in the plot2 object
plot2 <-xyplot(total ~ 1:length(total), type = "b", xlab = "Time", ylab = "No Votes", ylim = c(-1,4))
##Open a PNG device
png(file = paste("mapNo",count,".png", sep = ""),width=20, height=12, units="cm",bg="white", pointsize=20, res=300)
##Create two viewports for the two plots created above
pushViewport(viewport(layout = grid.layout(1, 2, unit(c(2, 1), "null"))))
##Print plot1 in the first viewport
pushViewport(viewport(layout.pos.col = 1, layout.pos.row = 1))
print(plot1, newpage = F)
upViewport()
##Print plot2 in the second viewport
pushViewport(viewport(layout.pos.col = 2, layout.pos.row = 1))
print(plot2, newpage = F)
upViewport()
##Close the device
dev.off()
##Update the count
count <- count + 1
}
}
The problem is that R crashes after 8 iterations, I suspect that somehow I am using up huge amounts of memory, but I really have no idea of what is going on.
EDIT2: I get a windows error message which says (translated from Germahn): The R for Windows front-end does not function any more
EDIT3: I have been monitoring the memory use from the windows task manager, and after 8 iterations the memory is almost used up completely.
EDIT4: I get the same error when using different graphics devices (png, jpeg, pdf). I was able to run the loop without using the viewports, so I am suspecting that this is related to the viewports.
Best, Thomas
