It's the average slope of the 50 day MA of about 1000 stocks over the past 10 years.
I calculated the slope using the percentage rise over 5,10,20,30,40 days ... it really seemed to smooth out at 40 days.
market.mktDays[didx].slope3 = 100*((market.mktDays[didx].SMA[0] - market.mktDays[didx-s1].SMA[0])/market.mktDays[didx-s1].SMA[0])/s1;
market.mktDays[didx].slope2 = 100*((market.mktDays[didx].SMA[1] - market.mktDays[didx-s2].SMA[1])/market.mktDays[didx-s2].SMA[1])/s2;
market.mktDays[didx].slope1 = 100*((market.mktDays[didx].SMA[2] - market.mktDays[didx-s3].SMA[2])/market.mktDays[didx-s3].SMA[2])/s3;
I wouldn't suggest that this is particularly novel ... but it looked pretty when it was first generated.