Triangular plot

http://www.google.com/imgres?imgurl=http://www.ex-parrot.com/~chris/tmp/talk-2004-06-15/end-of-2003.png&imgrefurl=http://www.ex-parrot.com/~chris/wwwitter/20050407-it_doesnt_matter_how_you_vote_either_way_your_planet_is_doomed.html&usg=__fkRdvkEKCxDVQ8YzYKl_Ko-iH0c=&h=627&w=653&sz=41&hl=en&start=5&zoom=1&um=1&itbs=1&tbnid=Sf0A22Ny39_0iM:&tbnh=133&tbnw=138&prev=/images%3Fq%3DTriangular%2Bplot%26um%3D1%26hl%3Den%26sa%3DN%26tbs%3Disch:1
This map illustrates three sets of data; the liberal democratic vote, labour vote as well as the conservative vote. Triangular plot maps are useful because comparisons can be made easily.