PRTBANDSDOWN

Syntax

PRTBandsDown

The instruction takes no parameters and no price argument. It returns the current value of the lower PRT Bands line on the chart's instrument and timeframe.

Formula

PRT Bands is a proprietary built-in channel indicator of the ProRealTime™ platform, and its internal formula is not published. PRTBandsDown exposes the lowest of its lines as a numeric series that can be compared against price or other variables. The exact values cannot be reproduced from a documented equation, unlike BollingerDown or DonchianChannelDown.

How it works

PRT Bands draws a multi-line channel around price, with an upper band, a lower band, and intermediate short-term and medium-term lines. PRTBandsDown retrieves the lower boundary of that structure on every bar.

The band acts as a dynamic support reference. While price trades inside the channel, the lower band marks the zone where declines have tended to stall. A close crossing under the band signals that price has left the channel to the downside, which channel-based strategies treat as a potential sell or short trigger, or as a stop level for existing long positions.

The value updates bar by bar together with the underlying indicator, so it can be stored in a variable, compared with CROSSES UNDER, plotted, or used inside screener and strategy conditions like any other built-in series. The companion instructions PRTBANDSUP, PRTBANDSSHORTTERM and PRTBANDSMEDIUMTERM return the other lines of the same channel.

Examples

Example 1, Marking downside breakouts with arrows (Indicator)

a = PRTBandsDown
if close crosses under a then
    // draw a red arrow above the breakout candle
    drawarrowdown(barindex, high + averagetruerange[14] / 2) coloured(255,0,0)
endif

Stores the lower band in a and draws a red downward arrow above any candle whose close crosses under it. The arrow is offset above the high by half the 14-bar average true range so it stays clear of the candle.

Example 2, Channel breakdown screener (ProScreener)

// Instruments closing below the lower PRT band
band = PRTBandsDown
breakdown = close CROSSES UNDER band
SCREENER[breakdown](((close - band) / band * 100) AS "% below band")

Lists instruments whose close has just crossed under the lower band and shows how far below the band they closed, in percent.

Example 3, Band breakdown as a short entry (ProOrder)

// Short the downside channel break, cover on return above the band
band = PRTBandsDown

IF NOT OnMarket AND close CROSSES UNDER band THEN
  SELLSHORT 1 CONTRACT AT MARKET
ENDIF
IF ShortOnMarket AND close CROSSES OVER band THEN
  EXITSHORT AT MARKET
ENDIF

Opens a short position when price breaks below the channel and closes it when price re-enters the channel from below.

Interpretation

The lower band is one piece of the PRT Bands structure. Reading it together with PRTBANDSUP shows the full channel width, and comparing price with the medium-term line indicates position within the channel rather than only breakouts.

Common errors and gotchas

• No parameters accepted. PRTBandsDown[20] or PRTBandsDown(close) will not compile. The instruction is a plain keyword with no period or price argument, its settings are internal to the platform.
• Proprietary calculation. The band cannot be recomputed manually or verified against an external formula. Strategies that must be portable to other platforms should use a documented channel such as Bollinger, Keltner or Donchian instead.
• Breakouts can be volatility spikes. A single close under the band during a news bar is not necessarily a trend change. Confirmation, such as a second close outside or a volume condition, reduces false triggers.
• Whipsaw around the band. In quiet markets price can oscillate across the band line, firing repeated cross conditions. Entry logic in strategies should track position state, as in the examples, rather than acting on every cross.

Related instructions

• PRTBANDSUP, the upper band of the same channel.
• PRTBANDSMEDIUMTERM, the medium-term line of the PRT Bands.
• PRTBANDSSHORTTERM, the short-term line of the PRT Bands.
• BollingerDown, lower Bollinger band with a documented formula.
• KeltnerBandDown, lower Keltner channel line.
• DonchianChannelDown, lowest low channel boundary.
• AverageTrueRange, used in the example to offset drawings from price.
• DRAWARROWDOWN, drawing command used to mark breakdown bars.