100 * (x[t] / x[t-k] - 1) - TA-Lib's ROC.
Lookback k. TA-Lib default is 10.
https://screamer.readthedocs.io/en/latest/ for the Python reference and full details.
100 * (x[t] / x[t-k] - 1) - TA-Lib's ROC.