I posted this in another place. Sorry for that. Hope I got it right this time. 

Can you give me a formula for when a stock price dropped significantly? The kind of fall you would see after a terrible earnings report. Seriously gapping down. 

Maybe the type of situation where the stock price dropped by 20% yesterday. Maybe that could be adjusted to 10% or 40%.  Or maybe between 20% and 50%. Something like that.

Thanks in advance

I'm going to start with the more traditional versions of a gapping down formula where open is at least 20% below the previous close.

O <= .8 * C1

Where the open is at least 20% below the previous low.

O <= .8 * L1

Where the high is at least 20% below the previous close.

H <= .8 * C1

And where the high is at least 20% below the previous low.

H <= .8 * L1

In all of the above cases there is some sort of gap between the previous bar and the current bar. be it just from the previous close and current open or the entire candle.

You also mentioned dropping by 20% yesterday? That would generally be either a percent change from the close before that.

C1 <= .8 * C2

Or from the open of that same bar.

C1 <= .8 * O1

Note that the .8 in all of these formulas is what represents the 20% drop. It is calculated by subtracted the desired percentage divided by 100 from 1. So the 20% is 1 - (20 / 100) = .8. This would mean you would use .9 for 10%, .6 for 40% or .5 for 50%.