Cold Blood Index
The Cold Blood Index (CBI) can determine whether a strategy has
become unprofitable due to a substantial market change. For this purpose, live
trading drawdowns are daily compared with the profit-loss curve from the last backtest. The probability of encountering such a drawdown is calculated based on the algorithm published on Financial Hacker, and displayed in the trade log and on the status page. A drawdown of low probability indicates a deviation from the backtest due to a biased test or a market change. This information can be used for deciding whether it's better to stop trading the system, or to continue it in cold blood.
The probability is calculated with the following function:
CBI (var* Data, int Length, int Shuffle, var Depth, int Width, int Horizon): var
Returns the probability in percent (0..100) of encountering a drawdown of the given Depth and Width within a given time Horizon. For this, the drawdown is compared with the Data array that
is supposed to contain a profit/loss curve from a backtest or a previous trading session.
Probability in percent (0..100).
A low probability (less than 2%) indicates a deviation from the backtest.
||Data array with profit/loss values, f.i. from the
pnl.dbl curve stored in a backtest.
||Length of the data array, positive for an array in time descending order and negative for ascending order.
||Number of shuffled profit/loss curves to evaluate, or 1
for only evaluating the original curve. The returned probability is
calculated from the original and the shuffled curves.
||Drawdown depth, the difference of an equity or balance peak with the subsequent equity or balance valley,
in the same scale as the values in the Data array.
||Drawdown duration, the time distance between the highest peak and the subsequent
deepest valley, in the same units as the time distance of the points in the
Data array, usually bar periods or days.
||Live trading time in in the same units as the Data array, usually bar periods or days. Must be equal or above Width and smaller than Length.
Drawdown scale for the automatic CBI calculation in [Trade] mode (default = 1 = no scaling). The drawdown depth is divided by this scale factor for calculating the CBI.
Current CBI value in [Trade] mode (see remarks).
- Enough data should be available for meaningful results. Have
Length >> Width and Horizon
- ReturnCBI is automatically calculated and displayed in [Trade] mode
when Verbose is at 2 or above, when a backtest profit/loss curve
(*pnl.dbl) is present in the Data folder, when trades have been opened and
when a drawdown longer than 3 days was encountered. It is recalculated once per day.
The Shuffle parameter is 5% the
Montecarlo variable, so the default is 10 (original plus 9 shuffled
curves). In [Test] mode the CBI is recorded in the
.log file. Note that the CBI in live trading is only valid
when the trade volume is the same as in the backtest and when no trades are
resumed from previous sessions.
- Use seed to get always the same result when
shuffling is used.
- When the volume per trade is different to the backtest, use either
volume-independent PIPRETURN curves or set CBIScale the current average trade volume divided by the average trade volume in the backtest (see example).
- The Z systems display the CBI on their trade status pages. For this, run a backtest with the
slider at the same position as in live trading at session start. When the
system runs on a VPS, make sure that the *.dbl file from the backtest is copied to the
Data folder on the server.
//scale drawdowns for CBI according to invested capital
var Invest = slider(1,5000,0,10000,"Investment","Invested capital");
static var InitialInvest = 0;
if(is(INITRUN)) InitialInvest = Invest; // store the initial investment that was also used in the backtest
if(InitalInvest > 0) CBIScale = Invest/InitialInvest;
//Check the Cold Blood Index at a Z12 Drawdown of $800 in
//$500 in the last 60 of 100 trading days
var* PnLs = file_content("Data\\Z12_pnl.dbl");
int Length = file_length("Data\\Z12_pnl.dbl")/sizeof(var);
var P = CBI(PnLs,-Length,1,500,60,100);
printf("\nCBI = %.0f%%",P);
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