If no output is requested, plot the bollinger bands of the
asset. If output is requested, return the values for the
bollinger bands. If given, alpha is the weighting power of the
moving average; 0 (default) is the simple moving average, see
movavg
for the full definition. width is the number of
standard deviations to plot above and below the moving average
(default: 2).
See also: movavg, candle, dateaxis, highlow, pointfig.
Package: financial