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)),
 )?;