Use the latest version of Circos and read Circos best practices—these list recent important changes and identify sources of common problems.
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A track's background can be colored using <backgrounds> block and graduated using <axes> block.
<plot> ... # axes <axes> <axis> ... </axis> <axis> ... </axis> ... </axes> # backgrounds <backgrounds> <background> ... </background> <background> ... </background> ... </backgrounds> </plot>
Much like ticks, axes are defined in groups. Each group can be spaced either with absolute or relative spacing. You can provide an axis line at specific positions and, for groups which have spacing, skip some positions.
spacing- absolute or relative spacing of the axis
position- fixed position (or positions) for axes
position_skip- fixed position (or positions) to skip when drawing axis lines
y0- absolute or relative start of axis lines
y1- absolute or relative start of axis lines
color- color of axis lines
thickness- thickness of axis lines
<axes> # Show axes only on ideograms that have data for this track show = data thickness = 1 color = lgrey <axis> spacing = 0.1r </axis> <axis> spacing = 0.2r color = grey </axis> <axis> position = 0.5r color = red </axis> <axis> position = 0.85r color = green thickness = 2 </axis> </axes>
Background elements are color rings within the track boundary between
y1 limits. Multiple background elements can e used to give the track a striped or gradated look. Each element is defined as a separate <background> block, which are processed in order of appearance.
y1 limits are not specified, the boundaries of the track are used.
<backgrounds> # Show the backgrounds only for ideograms that have data show = data <background> color = vvlgrey </background> <background> color = vlgrey # the "r" suffix indicates position relative to track data range y0 = 0.2r y1 = 0.5r </background> <background> color = lgrey y0 = 0.5r y1 = 0.8r </background> <background> color = grey # if y1 is not specified, the plot maximum is used (e.g. y1=1r) y0 = 0.8r </background> </backgrounds>
In most cases, the purpose of a <plot> block is to show data. Axes and backgrounds associated with a <plot> block that contains data will always be drawn under the data.
To precisely control whether axes and backgrounds are placed below or over the data, use a bare <plot> block (one without
type parameter). Doing so will use the <plot> block to draw the axes and background only, without any data.
<plot> # no file or type parameter r0 = 0.5r r1 = 0.75r # use z to determine whether this block (axes,background) will be # drawn on top of other plot blocks. z = 10 <axes> ... </axes> <backgrounds> ... </backgrounds> </plot>
Here is an example of how to use this kind of axes <plot> block. Depending on the
z parameter of the axis <plot> block, the axes are drawn above or below the data in the second block. By setting the axis color to have transparency (
grey_a3), the axes will blend with the histogram bins when drawn on top of then.
<plots> # positions are inherited by both <plot> blocks r0 = 0.5r r1 = 0.8r <plot> z = 10 # drawn on top of data # z = -10 # drawn below data <axes> <axis> spacing = 0.1r color = grey_a3 thickness = 1 </axis> </axes> </plot> <plot> # default z value is 0 type = histogram file = data.txt </plot> </plots>