london_animation.R

# Animated Choropleth of Population Density Change

# read data with population
df        = read.csv('http://goo.gl/yJQs8');
names(df) = sub('Persons.', '', names(df));

# read data with areas
df_area   = read.xls('http://goo.gl/UJbKE', 
              sheet = 2, pattern = 'Code')[,c('Code', 'Total')];
df_area$Total = with(df_area, sapply(as.character(Total), sub, pa = ",", r = ''))
df_area$Total = with(df_area, sapply(Total, as.numeric))

# merge the two and compute population density              
df = merge(df_area, df, by.x = 'Code', by.y = 'Area.Code');
df[,4:ncol(df)] = df[,4:ncol(df)]/df$Total*10;

.breaks = seq(0, 4000, by = 500);
library(animation);                                          
saveMovie(for (i in 4:ncol(df))
   print(plotChoropleth(.poly = london, .df   = df,   
     id1 = 'ons_label',  id2 = 'Code', 
     field = as.character(names(df)[i]),   
     colpal = 'Oranges', .breaks = .breaks)),
     clean = T)