Optional X Grid Lines

# grid_x_lines.js

var chart = c3.generate({ data: { columns: [ ['sample', 30, 200, 100, 400, 150, 250] ] }, grid: { x: { lines: [ {value: 1, text: 'Lable 1'}, {value: 3, text: 'Lable 3', position: 'middle'}, {value: 4.5, text: 'Lable 4.5', position: 'start'} ] } } });