Mathematics of valuation of currency

there are various factors which affects the value of currency of any country...........
which are as follows
1)demand & supply
2)politics
3)interest rates
4)economic growth
5)commodity prices

in these factors gdp, interest rates, politics is directly related to the internal matters of the country.......
now remaining two factors...........

some examples related to few countries currency

there are few countries whose currency is highly influenced with commodity prices
1)australian dollar
2)canadian dollar
3)new-zeland dollar

canadian dollar is highly influenced with crude oil prices whenever there is any rise in the price of crude oil the value of canadian dollar also goes up but crude oil priced in US $ so when the opec countries rise the price of crude oil its mean the value of US $ decreasing
so we can say there is a inversly propostional relationship with US$ and canadian dollar.....
while australia is the third largest producer of gold the australian dollar has the positive corelation with gold price up to 84% this is the data between the 1999 to 2008