Update on Improved Currency Strength Indicator

Following on from my previous post I have now slightly changed the logic and coding behind the idea, which can be seen in the code snippet below

%  aud_cad
mse_vector(1) = log( ( current_data(1,1) * ( aud_x / cad_x ) ) / current_data(2,1) )^2 ;
%  xau_aud
mse_vector(46) = log( ( current_data(1,46) * ( gold_x / aud_x ) ) / current_data(2,46) )^2 ;
%  xau_cad
mse_vector(47) = log( ( current_data(1,47) * ( gold_x / cad_x ) ) / current_data(2,47) )^2 ;

Essentially the change simultaneously optimises, using Octave's fminunc function, for both the gold_x and all currency_x geometric multipliers together rather than just optimising for gold and then analytically deriving the currency multipliers. The rationale for this change is shown in the chart below,

which shows the optimisation errors for the "old" way of doing things, in black, and the revised way in blue. Note that this is a log scale, so the errors for the revised way are orders of magnitude smaller, implying a better model fit to the data.

This next chart shows the difference between the two methods of calculating a gold index ( black is old, blue is new ),

this one shows the calculated USD index

and this one the GBP index in blue, USD in green and the forex pair cross rate in black

The idea(s) I am going to look at next is using these various calculated indices as inputs to algorithms/trading decisions.