Usage
circos.trackText(
factors,
x, y,
labels,
track.index = get.cell.meta.data("track.index"),
direction = NULL,
facing = c("inside", "outside", "reverse.clockwise", "clockwise",
"downward", "bending", "bending.inside", "bending.outside"),
niceFacing = FALSE,
adj = par("adj"),
cex = 1,
col = par("col"),
font = par("font"))