GEN: comparing systems (profit the best?) - Sharpe Ratio?

["MORIMOTO, Kozo (FinAssets)" <Kozo.MORIMOTO@xxxxxxxxxxxxxxxxxxxxx>]

Talking about comparing systems and whether the overall profit is the best
indicator, can someone tell me how to calculate the Sharpe Ratio for a
trading system?  I read the oodles of info on it, but it does something like
annualised return etc etc.  Say my system generated 900 points over 13
years, how do you translate 900 points to annualised returns?  How do you
get standard deviation of annualised returns?  How about the requirement of
riskless annualised return figure when the riskless annualised return is
constantly changing?

Or for trading system analysis, is Sharpe Ratio useful as a chocolate
teapot?

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