Machine learning in trading: theory, models, practice and algo-trading - page 2535

 

Returns (returns) are for theorists. The practitioners have their own methods.

 
Aleksey Nikolayev #:

sampling of price logarithm increments

The price of currencies does not change many times, why does it need the logarithm? But the increments do change.
 
Aleksey Nikolayev #:

Still try sampling d[i]=log(bid[i]/bid[i-1])=log(bid[i])-log(bid[i-1]).

You can also try approximation without logarithms d[i]=bid[i]/bid[i-1]-1

Surprisingly, these formulas do not work

bid[i]/bid[i-1]-1 log(bid[i]/bid[i-1])


And the result is very close, even if you squint your eyes you can't see the difference. The axes are offset by a few pixels. I checked it several times.

 
Aleksey Nikolayev #:

Returns (returns) are for theorists. The practitioners have their own methods.

Then I do not understand what we are talking about.
 
Maxim Dmitrievsky #:
Then I do not understand what we are talking about

As a theorist, I don't really understand either.

 
Rorschach #:

And the result is very close, even if you squint your eyes do not see the difference. The axes are offset by a few pixels. I checked it several times.

It should be so, because with small x approximately log(1+x)~x. In this case x=bid[i]/bid[i-1]-1

Rorschach #:

Surprisingly, these formulas do not work.

Perhaps the well-known thick-tailed effect of the returnee distribution is manifesting itself. Larger returnee values appear more often than they should in the case of a normal distribution.

 
Did anyone pay attention to the age on the Lag plot? This is the quotient posted a few pages ago.
 
secret #:
The price of currencies does not change by times, why does it need a logarithm? But the increments do.

One reputable scientist wrote that the price must be logarithmic, and all theorists blindly continue to do so.

 
Aleksey Nikolayev #:

One reputable scientist wrote that the price must be logarithmic, and all theorists blindly continue to do so.

He must have written about shares.
 
secret #:
So he must have written about stocks.

I haven't read it, but the Bleck-Scholes formula is derived from it and it doesn't say it's only about stock options. Although of course it is not exactly true for anything, it is used as a starting point for all option theories.

Reason: