<<results=tex>>=
    mrrs <- positions
    mrrs <- mrrs[mrrs$latest & mrrs$frm,]
    mrrs <- mrrs[mrrs$evaluator %in% c('CorpusEvaluator', 'LinearEvaluator.nocoverage'),]
    mrrs$evaluator <- droplevels(mrrs$evaluator)
    mrrs <- daply(mrrs, .(project, evaluator), function(x) mean(1/x$position))
    colnames(mrrs) <- format_name(colnames(mrrs))
    rownames(mrrs) <- format_name(rownames(mrrs))
    print(xtable(mrrs, digits=3, caption='Mean reciprocal ranks for corpus and combined approaches on each project', label='tab:combined_ranks'), table.placement='tb')
@
