This function employs rc.plot.histogram to plot heat-map. Every row of Data will be plotted as heat-map in one track. The column names of Data must be the chromosome ids.
If color.gradient is not NULL, the data will be scaled to positive integers in the range of 1~length(color.gradient) to index the colors in vector color.gradient. If color.gradient isNULL, the input Data must be a matrix of colors or anything that can be converted to colors.