\begin{figure}[t]
    \centering
<<fig=TRUE,height=3>>=
    cumulative_coverage <- reports
    cumulative_coverage <- cumulative_coverage[is.finite(cumulative_coverage$coverage.related.cummean),]
    cumulative_coverage$display_order <- unlist(by(cumulative_coverage, cumulative_coverage$project, function(x) order(order(x$bug_number))))
    cumulative_coverage <- melt(cumulative_coverage, id.vars=c('project', 'bug_number', 'bug_id', 'display_order'), measure.vars=c('coverage.related.cummean', 'coverage.unrelated.cummean'))
    cumulative_coverage$project <- format_name(cumulative_coverage$project)
    cumulative_coverage$variable <- format_name(cumulative_coverage$variable)
    cumulative_coverage$dummy <- format_name('coverage.overall')
    fig <- ggplot(cumulative_coverage, aes(display_order, value, linetype=variable)) +
        geom_line() +
        facet_grid(dummy ~ project, scales='free') +
        labs(x='Bugs ordered by report date', y='Coverage') +
        theme(axis.text=element_text(colour='black'),
              axis.text.x=element_text(angle=90),
              axis.title.y=element_blank(),
              legend.position='bottom',
              legend.title=element_blank(),
              panel.border=element_rect(colour='black', fill=NA)
        )
    print(fig)
@

    \caption{Cumulative running mean coverage in methods related and unrelated to a bug}
    \label{fig:cumulative_coverage_over_time}
\end{figure}
