Currency Index Indicator

The currency index represents the change in one currency by reference to all other
foreign currencies. The index is calculated by taking the average of the variations
in one currency by reference to the others. Represented in graphical form, it allows
for easy visualization of the individual trends in each currency.
The index of the currencies is a simple arithmetic average of the variation in each pair.
For each index, to have fixed the value 100 on 1 January 2000.