session.*

True on the first bar of each trading session and false on every other bar. It is the bar to reset anything that is measured per session: the day's high and low, a running volume, a count of trades.

session.isFirstBar: series bool

Type

series bool

First value

bar 0

version 1
study("Session high and low", overlay = true)

// The session's own first bar where the host states session hours,
// otherwise the first bar of each calendar day.
firstBar = orElse(session.isFirstBar, bar.isFirst or not date.isSameDay(time, time[1]))

var dayHigh = none
var dayLow = none
if firstBar
    dayHigh = high
    dayLow = low
else
    dayHigh = max(dayHigh, high)
    dayLow = min(dayLow, low)

plot(dayHigh, "Session high", lime, style = "step")
plot(dayLow, "Session low", red, style = "step")

Remarks. It is the first bar delivered inside the session's hours, so a session that opened late still has a first bar. The oldest bar of the chart counts as a first bar too when the data starts in the middle of a session, which makes the first session on the chart a partial one. A bar outside the session's hours has false.

It comes from the session hours in the instrument's record, read in the instrument's timezone. When the host states no session for the instrument, the value is none, and an if on it never runs. That is why the example wraps it in orElse(): where no session hours are stated, it falls back to a change of calendar day, which is the same thing for an NSE session.

The /trading chart and Backtest panel state the instrument's regular hours from the platform's market calendar, the same hours for every day on the chart, so a special session outside them, such as an evening session on a holiday, has no first bar there. On a chart whose timezone you have set to one other than the exchange's, the chart states no session at all rather than hours read in the wrong zone, and the value is none.

See also. session.isLastBar, bar.isFirst, vwap()

True on the last bar of each session's schedule. It is worked out from the scheduled close, not from the arrival of the next bar, so it is known while that bar is still running. On a 5 minute NSE chart it is the 15:25 bar. On a day when trading stops early, the scheduled last bar never arrives, so no bar of that day has it true.

session.isLastBar: series bool

Type

series bool

First value

bar 0

version 1
strategy("Intraday only", overlay = true, product = "intraday", fillOn = "close")

// The session's last bar where the host states session hours,
// otherwise the last fifteen minutes of the NSE day.
squareOff = orElse(session.isLastBar, session.isIn("1515-1530", "Asia/Kolkata"))

fast = ema(close, 9)
slow = ema(close, 21)

if crossUp(fast, slow) and not squareOff
    buy()
if crossDown(fast, slow) or squareOff
    close()

Remarks. Waiting for the next session's first bar to flatten is too late: by then the position has been carried overnight. Watch the fill rule too. With the default fillOn = "nextOpen", an order decided on the last bar fills at the next bar's open, which is the next session's first bar. The example declares fillOn = "close" so the exit fills at the close of the bar that decided it. The other way is to decide earlier, with a window such as session.isIn("1515-1530"), and keep the default fill.

It needs the chart's interval as well as the session hours, to know which bar slot is last. When the host does not state both, the value is none, which is why the example falls back to a window. The window names its zone so it reads Indian time on any host. A strategy running from the Strategies panel is refused when it reads session.isLastBar, so for a deployed strategy use the window alone.

See also. session.isFirstBar, close(), bar.isLast

True when the bar falls inside a window of clock times you write, such as "0915-1000" for the first forty-five minutes of the NSE session or "1430-1530" for the last hour. Use it to trade only part of the day, to shade a period, or to hold a range while it forms. It needs nothing from the host except a timezone, so it works on every chart.

session.isIn(spec: string, zone?: string = chart.timezone) -> series bool

Returns

series bool

First value

bar 0

version 1
study("Entry window", overlay = true)

window = input("0930-1445", "Entry window")
inWindow = session.isIn(window)

fast = ema(close, 9)
slow = ema(close, 21)
crossed = crossUp(fast, slow)

if inWindow and crossed
    signal("BUY")
background(inWindow ? none : fade(gray, 92))

The spec string is "HHMM-HHMM", with an optional list of days after a colon.

Remarks. The window starts at the first time and stops before the second: a bar that opens at 15:30 is outside "0915-1530", and the 15:25 bar is inside. The test uses the bar's opening time, time. Two windows written back to back, such as "0915-1200" and "1200-1530", cover every minute exactly once. An end of 2400 means midnight at the end of the day.

Days are numbered 1 for Monday through 7 for Sunday, the same as date.dayOfWeek(). For a window that crosses midnight, the day list names the day the window opened on: "2300-0100:1" covers Monday 23:00 to Tuesday 01:00.

The times are read in the chart's timezone unless zone names another IANA zone (the standard Area/City form), such as "Asia/Kolkata". Where no timezone is known, the result is none unless you pass zone. The /trading chart, its Backtest panel and a strategy running from the Strategies panel all state one. A zone the host does not know stops the script with OS6005; abbreviations such as "IST" are not zone names.

A spec that does not follow the form above, such as "9:15-15:30", is not caught by the compiler and matches no bar: the result is none, so a condition built on it never holds. Check the spelling when a window never lights up.

See also. session.isFirstBar, date.hour(), chart.timezone