Chris: I'm not sure what you have in mind. Envelopes for moving averages can
be as wide or narrow as you set them. If you want to set envelopes 5 points
above and below an MA, the distance between the envelopes will be 10 points,
and it won't change. The distance between the envelopes wouldn't depend on
the behavior of the price of the stock -- unless you added another factor to
the envelopes to make them expand and contract (volatility, for example).
Bollinger bands would expand and contract, for example. (Standard deviation
in Bollinger bands is a measure of volatility). So would Donchian channels,
which are based on previous highs and lows. Did you have Bollinger bands in
mind?
If so, try this:
output="bollbandrange.lst";
issuetype=common;
exchange nyse,nasdaq,amex;
float bolbandlower, bolbandupper;
bolbandlower:=movavg(0,20,cl)-(StDev(0,-19)*2);
bolbandupper:=movavg(0,20,cl)+(StDev(0,-19)*2);
if bolbandupper-bolbandlower >=10 then
println Symbol, " ,", "Band range: ", bolbandupper-bolbandlower:0:3,
" Close: ", Close(0):0:3;
endif; |
