Reforming a graph as well as a set of data

Hello,

At the moment I am trying to manipulate some data of a shock absorber. My goal is to find the bump and rebound damping rates from the area of a graph, however to achieve this I need to reform my data (or remove the effect caused by the spring in other words) and was hoping to get some advice.

The graph I have at the moment from the data is this:

Now my goal is to lower the center point to 0, to have the x axis cut through the graph, I have an idea of how to do that (basically I have the means to find the spring force at that neutral position, hence I can remove it partly as a factor.

The difficult part however is to rotate the data, not just the graph, to a parallel position, as I'll need to use the trapz for Force>0 and Force<0 (hence requiring the graph starting position to be lowered to 0). A thought I had was to create a vector symbolizing the spring force and subtracting it from the data, that however brings a lot of problems such as starting and ending the vector at a correct point (as well as changing the direction, considering that the original graph represents cycles) so that the subtraction wouldn't create more errors. Add to that there are 5 more experiments such as this that have to be reformed as well, so ideally a more efficient method (if there is such) would be preferred.

Hence the final question: Is there a more simple way of reforming the data (which is basically removing the spring effect of the shock absorber) to find the damping rates?

Thanks!

[bym]

can you post your data (or a subset?)