Simon Jackman calculates ideal point estimates based on non-unanimous roll calls: http://jackman.stanford.edu/ideal/currentSenate/x1.pdf http://jackman.stanford

Simon Jackman calculates ideal point estimates based on non-unanimous roll calls: http://jackman.stanford.edu/ideal/currentSenate/x1.pdf http://jackman.stanford.edu/ideal/currentSenate/x1.pdf I think his R source is available too.