R code to create a map time lapse with ggplot and ffmpeg

time lapse.R

setwd("C:/Documents and Settings/bhoung/My Documents/time/")
require("ggplot2")
require("maptools")
gpclibPermit()

# read in spatial data - from the ABS (Australian Burea of Statistics) website

shp <- readShapeSpatial( fn = "C:/Documents and Settings/bhoung/My Documents/asgc/SLA11aAust", verbose = TRUE, delete_null_obj=TRUE)
summary(shp)
list_names = names(shp)
shp$melb = substr(shp$SLA_CODE11, start=1, stop=3)

# create a subset of the spatial data, take only the state Victoria
vic <- shp[which(shp$STATE_CODE==2),]

# create a subset of the spatial data, take only the city Melbourne
melb = shp[which(shp$melb=="205"),]

# fortify data, so that ggplot can map it.
u <- unique(melb$SLA_CODE11)      
out <- fortify.SpatialPolygonsDataFrame(shp[u,], region="SLA_CODE11")

# read in unemployment Small Area Labour Market data from DEEWR 
unemp <- read.csv("C:/Documents and Settings/bhoung/My Documents/Dropbox/business cycle/excel/unemployment0810.csv")

# merge unemployment with spatial data
m <- merge(melb, unemp,  by.x="SLA_5DIGIT", by.y="SLA.Code", all.x=TRUE)

# merge fortifed spatial data with spatial data that now contains unemployment data
m2 <- merge(out, m, by.x="id", by.y="SLA_CODE11", all.x=TRUE)
names <- names(unemp)                     

# counter
j = 1

for (n in 17:28) {

     # create different categories/shadings of unemployment  
     m2$rate <- cut(as.numeric(m2[,n]), breaks = c(seq(0, 12, by = 2)))

     # choose colours
     cbbPalette <- c("#E3D1E7","#D7B5D8","#DB8DC3","#DF65B0","#D63B83","#CE1256")

     #ggplot code
     map = ggplot(m2, aes(long, lat, group = group)) +
     geom_polygon(aes(fill = rate), colour = alpha("white", 1/2), size = 0.2) +
     scale_fill_manual(values=cbbPalette, name = "Unemployment\nRate") +
     ylab("Latitude") +  xlab("Longitude")

     #get the date of the unemployment data to use in labeling map

     name <- names(m2)[n]
     g1 <- map + coord_map() + opts(title = name)
     ggsave(plot = g1, filename=paste('melb unemp', j, '.jpg', sep = ''), height = 5, width = 6)
     j = j + 1

}                

#./ffmpeg -f image2 -r 5.5 -i /Users/brendanhoung/Dropbox/time/melb\ unemp%d.png -b 800k unemp.mp4