r - Choropleth world map -

i have read many threads , articles , keep getting errors. trying make choropleth? map of world using data have global terrorism database. want color countries on factor of nkills or number of attacks in country.. don't care @ point. because there many countries data, unreasonable make plots show data.

help appreciated , if did not ask correctly sincerely apologize, learning rules of website go.

my code (so far..)

library(maps) library(ggplot2) map("world") world<- map_data("world") gtd<- data.frame(gtd) names(gtd)<- tolower(names(gtd)) gtd$country_txt<- tolower(rownames(gtd)) demo<- merge(world, gts, sort=false, by="country_txt") 

in gtd data frame, name countries column "country_txt" thought use error in fix.by(by.x, x) : 'by' must specify uniquely valid column

if work, plot have seen on few websites.. have been working on long , have read many codes/other similar questions/websites/r handbooks etc.. accept incompetent when comes r gladly help.

building on nice work @jlhoward. instead use rworldmap has world map in r , has functions aid joining data map. default map deliberately low resolution create 'cleaner' look. map can customised (see rworldmap documentation) here start :

library(rworldmap)  #3 lines @jlhoward  gtd        <- read.csv("globalterrorismdb_1213dist.csv") gtd.recent <- gtd[gtd$iyear>2009,] gtd.recent <- aggregate(nkill~country_txt,gtd.recent,sum)  #join data map gtdmap <- joincountrydata2map( gtd.recent,                                 namejoincolumn="country_txt",                                 joincode="name" )  mapdevice('x11') #create world shaped window  #plot map mapcountrydata( gtdmap,                  namecolumntoplot='nkill',                  catmethod='fixedwidth',                  numcats=100 ) 

following comment @hk47, can add points map sized number of casualties.

deaths <- subset(x=gtd, nkill >0)  mapbubbles(deaths,            namex='longitude',            namey='latitude',             namezsize='nkill',             namezcolour='black',            fill=false,             addlegend=false,             add=true)