This snippet tracks and displays the current bar’s accumulated volume while the bar is still forming, instead of only showing the finalized volume after the bar closes. It solves the problem of estimating real-time activity on the current timeframe (for example, on volume bars or time-based charts) by updating the displayed value on each last-bar refresh.

if not isset($volumes[barindex]) then
$volumes[barindex] = 0
endif

if islastbarupdate then
diff=volume-$volumes[barindex]
$volumes[barindex]=$volumes[barindex]+diff
endif

return $volumes[barindex] coloured(“orchid”) style(histogram,2)

Code Logic

• $volumes[barindex]: Persistent per-bar storage (indexed by barindex) used to remember the accumulated volume value for each bar.
• isset(…): Checks whether the array element for the current bar already exists; if not, it initializes it to 0 to avoid undefined access.
• islastbarupdate: Ensures the update logic runs only when the platform refreshes the currently forming (last) bar, preventing unnecessary recalculation on historical bars.
• diff: Computes the incremental change as volume – $volumes[barindex], i.e., the newly added volume since the last update for this bar.
• $volumes[barindex] = $volumes[barindex] + diff: Adds only the incremental difference, keeping the stored value synchronized with the live volume feed without double-counting.
• return … coloured(“orchid”) style(histogram,2): Plots the tracked per-bar volume as a histogram with thickness 2 and the specified color for readability.