High-Frequency Volume Rate of Change (VROC)

Query intraday minute-bar VROC (Volume Rate of Change) for A-share securities via the market data service.VROC = (Volume - Volume_N) / Volume_N * 100, measuring volume momentum. Default period N=12. Positive values indicate volume expansion, negative values indicate contraction.codes: comma-separated security codes (e.g. '600000.SH,000001.SZ').interval: minute bar width — 1/3/5/10/15/30/60.starttime/endtime: 'YYYY-MM-DD HH: MM: SS' intraday range.