Quote from cnms2:
If I understood you correctly, you were asking how to determine the volatility beforehand. You can't.
On the other hand you'll see that price movements in the same direction with the next higher time frame (thrusts) usually exhibits less volatility / price rate of change, than retracements.
Hence it's better to "trade with the trend", as the conventional wisdom says. With the same stop size you'll get better price movement.
No, I'm not asking how to determine volatility beforehand, I'm asking how to find the trendiness of a market from the historical data. Imagine from the 2005 data, I know that S&P doesn't trend a lot, and the most trendy it can get from point A to point B would be 3 days and assume the 3 days trendiness value is 1. In the same period, Oil is more trendy, with a 3 days trendiness of 1.7 (just an example).
I hope I could use the 2005 data to apply on the 2006 trading methods. Or I hope I could use the last quarter's data to apply on the next quarter's trading strategies.
Now given that both markets have a high enough 3 days trendiness value to trade, the path they finish from point A to point B could be different. S&P could be up one day strong, do nothing the next day, and up another strong to complete the 3 days trend. This is a smooth 3 day trend. While Oil could be up one day strong, gapped down next day and trade lower due to some news, then gap up and run big on the third day due to another news to complete the 3 days trend.
Both S&P and Oil complete their relative path from A to B, but the way they complete the path are different. One is smooth, one is volatile.
I already know some ETers can measure trendiness of different markets based on the number of days a trend persist. I'm asking how would you measure the volatility within the 3 days trend from the past data, but not the volatility of the market itself.
I assume knowing how to measure the 3 days trendiness will help, but I'm open to some other clever methods.