I have a line chart, with two series on it.

When i use a primary and a secondary axis, by double clicking on one
serie, then on axis label, choosing Plot series in : "Secondary Axis",
my chart looks like :

[img]http://dl-1.free.fr/52616e646f6d49562419387a8ea88a5618bb38b30dba0d4bb4c5d2a6c70d
4493/2axis.JPG[/img]
(maybe it won't display, you have two lines and two axis, and the two
lines have not the same value at all)

But now, if i choose (for the FF serie) "Primary Axis", i get :

[img]http://dl-1.free.fr/52616e646f6d49566af22302b459651d538fdfb923076bb85e7ca84c907c
c280/1axis.JPG[/img]
(the two lines/series are now very close, expected a few points. Only
the FF serie has changed, the other one remained unchanged)

You can see that the data has been fitted to be near the ED serie, so
the left axis does not correspond to the actual values of FF serie.
Excel must have applied a transformation to the initial data...
My question is : what is the transformation of data that have been used
by Excel to "fit" the other serie ? I just checked that it is not a
linear rescalling, so i really don't know what Excel did compute to
have such a good fitting of data (actually I want to use the FF serie
to predict the ED one, so it could be of very great help to find the
answer...).

Many many thanks for your help !