library(ggplot2)

update <- c(2030, 3156)
original <- c(1414, 2523)
inegi <- c(2567, NA)

hom <- data.frame(year = 2008:2009,
           updates = update,
           original = original,
           inegi = inegi)


ggplot(hom, aes(factor(year), updates, group = 1)) +
    scale_colour_discrete("Source") +
    geom_line(aes(color = "SNSP")) +
    geom_line(aes(factor(year), original, color = "SNSP"),
linetype = 2) +
    geom_point(aes(factor(year), inegi, color = "INEGI")) +
    ylim(0, max(update)) +
    xlab("year") +
    ylab("number of homicides") +
    opts(title = "Discrepancies in Homicide Data for the State of Chihuahua") +
    annotate("text", x = "2009", y = 2523, label = "original SNSP",
             hjust = 0) +
    annotate("text", x = "2009", y = 3156, label = "updated SNSP",
             hjust = 0) +
    annotate("text", x = "2008", y = 2567, label = "INEGI",
             hjust = 1.06)