I want to make a plot with Gviz for my bedgraph tracks, bed files and gff annotation.

I have this command for plotting bedgraph tracks:

bg1 <-  DataTrack(
range = file,
name="gene", type = "histogram", fill.histogram = "magenta",
col.histogram = shade, window=-2, windowSize=2, 
cex.axis=0.8,
rotation.title=1,
cex.title = 1,
ylim =c(0,10),   genome ='species', min.distance= 5)

and then this one for plotting:

plotTracks(bg1, 
         from = start, to = end, background.title='white',
         col.axis='black', col.title='black', add=add,
         title.width = 0.9,
         transformation = function(x) {x/median(x)},
         main=paste0(capitalize(species), name), margin = 50, innerMargin = 20)

I cannot figure out how to make the height of the track shorter. I know there is the ylim =c(0,10) but this changing this keeps the height the same and changes only the range to which y can go, while want to change visually the height of the track on the graph.

Any help would be great.

Dan