State level unemployment in R

Question

This is a newbie question. I want to plot the state level unemployment in the US map. There have been profound discussions here and elsewhere about how to plot county level unemployment and the issues associated with it. The code looks intimidating to me. Is there a simple code out there which takes two columns, a state code and a factor variable indicating numeric intervals and yields a colored US map(based on the factor variable). A supplementary question is that if I need to go a little further and create similar plot but with unemployment rate in major cities of US how do I modify the code. Thank you in advance.

Answer 1

Here is a quick piece of code with comments explaining each step. Let me know if you have questions

# load libraries
library(XML);
library(ggplot2);
library(maps);
library(plyr);

# read the data from the bls website with correct column formats
unemp = readHTMLTable('http://www.bls.gov/web/laus/laumstrk.htm',
  colClasses = c('character', 'character', 'numeric'))[[2]];

# rename columns and convert region to lowercase
names(unemp) = c('rank', 'region', 'rate');
unemp$region  = tolower(unemp$region);

# get us state map data and merge with unemp
us_state_map = map_data('state');
map_data = merge(unemp, us_state_map, by = 'region'); 

# keep data sorted by polygon order
map_data = arrange(map_data, order);

# plot map using ggplot2

p0 = ggplot(map_data, aes(x = long, y = lat, group = group)) +
     geom_polygon(aes(fill = cut_number(rate, 5))) +
     geom_path(colour = 'gray', linestyle = 2) +
     scale_fill_brewer('Unemployment Rate (Jan 2011)', pal = 'PuRd') +
     coord_map();
#You may need to spell out the argument pal as pallete

Answer 2

Ramnath nailed this one. If you're still looking for other solutions, there's a decent example using other packages at the SAS-and-R blog.