Gopalakrishnan Range Index (GAPO)

How large the range of the last few bars is, on a logarithmic scale.

What it measures

The highest high minus the lowest low of the window, put through a logarithm and divided by the logarithm of the window length.

How traders read it

Higher values mean a more erratic market. Because it is in price units, the level differs between instruments: compare it with its own history on the same instrument.

Formula

GAPO = log(highest high − lowest low) / log(periods), over the last periods bars

For a currency pair the range is a small fraction of 1, so the logarithm and the value are negative. periods must be at least 2, since the logarithm of 1 is 0, and a window with no range gives no value.

Settings and output

Call: gapo(periods)

Setting	Chart default
`periods`: Periods	10

What you get: a number.

Warm-up: with gapo(10), it asks for 10 bars of history and a run-up of 1, and its first value came on bar 11 of the example data.

Chart

Gopalakrishnan Range Index (GAPO) drawn by its own code on example prices

The prices are made up, hourly, and the same on every page, so the chart shows how the indicator behaves, not how a market behaved.

In an algorithm

function onIntervalClose() {
  log("GAPO", gapo(10));
}