Bug: APO (Absolute Price Oscillator) calculation has incorrect EMA alignment

[forwardalex]

Bug: APO calculation has incorrect EMA alignment

Problem

APO (Absolute Price Oscillator) calculation in trend/apo.go does not properly align Fast EMA and Slow EMA before subtraction.

Root Cause

When computing APO = Fast EMA - Slow EMA, the two EMAs have different periods (default: 14 and 30). The Fast EMA starts producing valid values earlier than the Slow EMA, but they are subtracted without aligning them to the same time point.

Expected Behavior

Fast EMA should skip the first (slowPeriod - fastPeriod) values to align with Slow EMA before subtraction.

Fix

Add one line in trend/apo.go, after line 75:

// Skip the first (slowPeriod - fastPeriod) values to align with slow EMA.
cs[0] = helper.Skip(cs[0], apo.SlowPeriod-apo.FastPeriod)

Reference

Other indicators that correctly implement this pattern:

• momentum/ppo.go line 70
• trend/macd.go line 59