Use the latest version of Circos and read Circos best practices—these list recent important changes and identify sources of common problems.
If you are having trouble, post your issue to the Circos Google Group and include all files and detailed error logs. Please do not email me directly unless it is urgent—you are much more likely to receive a timely reply from the group.
Don't know what question to ask? Read Points of View: Visualizing Biological Data by Bang Wong, myself and invited authors from the Points of View series.
You can add a radial grid to any set of tick marks. Grids are drawn on top of highlights, but behind all other data.
The radial start and end position of the grid lines can be controlled globally within the <ticks> block, or locally, within each <tick> block.
show_grid = yes <ticks> grid_start = 0.5r grid_end = 0.975r grid_color = black grid_thickness = 2p ... <tick> spacing = 1u ... grid = yes grid_color = grey grid_thickness = 1 grid_start = 0.55r grid_end = 0.95r </tick> <tick> spacing = 5u ... grid = yes grid_color = dgrey grid_thickness = 2 grid_start = 0.6r grid_end = 0.925r </tick> <tick> spacing = 10u ... grid = yes grid_color = black grid_thickness = 2 </tick> </ticks>