search for: millibar

Hi I had a look at the help and previous discussions but I am still unable to solve these issues: 1 I have a set of air pressure data. I would like to plot a and b (both about 980-1000 millibar) and c, the difference (around 0-8 millibar). I use axis (4) to create a new axis (to the right) but I do not know how to assign c to the new axis which currently features the same values as the first axis. So, how do I show a, b and c in the same plot with different scales (one for each y-axis)?...