let x_labels = vec!["< 1", "1-3", "3-6", "6-9", "> 9"];
        let mut data: Vec<usize> = Vec::with_capacity(x_labels.len());
        data.push(days.iter().take_while(|&&days| days < 1).count() as usize);
        data.push(days.iter().skip_while(|&&days| days < 1).take_while(|&&days| days < 3).count());
        data.push(days.iter().skip_while(|&&days| days < 3).take_while(|&&days| days < 6).count());
        data.push(days.iter().skip_while(|&&days| days < 6).take_while(|&&days| days < 9).count());
        let max_tickets: usize = *data.iter().max().unwrap();

        chart
            .configure_mesh()
            // Don't show a grid for the x axis
            .disable_x_mesh()
            // Make the y axis grid be light gray
            .line_style_1(&WHITE.mix(0.3))
            .x_desc("Biggest gap in days")
            .y_desc("Interaction Count")
            .axis_desc_style(("sans-serif", 15).into_font())
            .draw()?;

        chart.draw_series(
            Histogram::vertical(&chart)
                .style(RED.mix(0.5).filled())
                .data(x_labels.iter().flat_map(|x| category.get(x)).zip(data)),
        )?;