As far as I can tell, there is no good way to rotate the Y-axis in gnuplot. Making your own label is a PITA and doesn't look right; if anyone knows how to get the position exactly right I'll add it to this post.
The best I can come up with is to rotate the output in the final postscript.
If you want to do this, you simply add a translate into your output postscript as per below. Just add it to the line above the line that has your Y-axis string starting it.
--- ./contour.eps 2005-05-11 12:12:49.700892853 +1000 +++ contour-ok.eps 2005-05-11 12:12:42.404017942 +1000 @@ -23144,8 +23144,10 @@ LTb 6426 2620 M gsave 0 setgray +currentpoint gsave translate 90 rotate 0 0 M (Latency \(us\)) Cshow grestore +grestore 1.000 UP grestore % colour palette end stroke
Conversion to a bitmap is pretty crappy, but might work for some situations, like say, posting here.
That's a graph of how packet latency varies with different applied loads (load applied and data gathered via a distributed benchmark we wrote). That thin solid line in the middle shows that by and large, for this particular test latency doesn't vary that much with applied load. The secondary trend is latencies going up overall as the load gets higher.