For symbol CSCO, I am trying out the C# code found here:
http://www.risk256.com/code/Options.cs
I call the THETA function:
//Current information!
double dividendyield = 0.0328;
double riskfreerate = 0.0024;
double stockprice = 30.35;
double strikeprice = 32;
double yearsexpiration = (double)30 / (double)365; //18 NOV 16 Expiration
double knownoptionprice = (1.83 + 1.87) / 2;
double vol = Formulas.Formulas.BlackScholesImpliedVol(knownoptionprice, strikeprice, stockprice, yearsexpiration, riskfreerate, dividendyield, Formulas.Formulas.PutCallFlag.Put);
double theta = Formulas.Formulas.BlackScholesTheta(strikeprice, stockprice, yearsexpiration, vol, riskfreerate, dividendyield, Formulas.Formulas.PutCallFlag.Put);
I return this value: -3.077
When looking in TOS in the PUT column(Theta value) for strike 32, I find: -0.01
If -3.077 is the % value, it would be calculated like this:
-0.0377 * ((1.83 + 1.87) / 2) = -0.0697
I wonder if -0.0697 is ment to be the theta value/day. It is a very big difference vs TOS?