How to keep a running total across bars

Declare the total with static and add to it with :=. An ordinary declaration is made again on every bar, so an ordinary total starts again on every bar.

indicator("Running total of volume", "cumvol", false)

static float total = 0.0
total := total + volume

plot(total, title = "Total", color = color.blue)

static is the only keyword that makes a value persist across bars. A declaration opening var does not compile.

If the total should reset each session

Test session.isfirst and seed from the bar’s own value instead of from the previous total. That is the same shape the built-in cumulative delta uses: it seeds from zero on a session’s first bar and from the previous bar otherwise.

indicator("Volume so far this session", "sessvol", false)

static float total = 0.0
if session.isfirst {
    total := volume
} else {
    total := total + volume
}

plot(total, title = "Session volume", color = color.blue)

If you are accumulating a plain series

talib.cum accumulates a series as the script advances, with no length argument and no declaration of your own.

talib.cum(series float source) → series float

indicator("Cumulative volume", "cum", false)
plot(talib.cum(volume), title = "Total", color = color.blue)

Reach for it in place of a static total unless you need the reset above: talib.cum takes no condition, so you cannot restart it.

If the total you want is cumulative delta

Do not write it yourself. orderflow.cvd adds each bar’s delta to a running total, restarts from zero on the first bar of a session, and leaves the total unchanged on a bar whose delta is na rather than breaking it.

orderflow.cvd() → series int

indicator("Cumulative delta", "cvd", false)
plot(orderflow.cvd(), title = "CVD", color = color.blue)

The failure to watch for

Every orderflow value reads na on a bar with no footprint data behind it. A total of your own that adds orderflow.delta directly will carry that na forward. Guard the addition, or use orderflow.cvd, which already does.

See Values that persist across bars and Orderflow.