TRIX was created by Jack Huton. It is a momentum indicator that displays the percent rate-of-change of a triple exponentially smoothed moving average of a security's closing price. It it is designed to filter out price movements that are considered insignificant or unimportant. The indicator can be used to anticipate turning points in a trend through its divergence with a security's price.
x is the period which must be an integer.
A 15 period TRIX can be written as follows.
100 * (XAVG(XAVG(XAVGC15, 15), 15) / XAVG(XAVG(XAVGC15.1, 15), 15) - 1)
Read more about Triple Exponential Average (TRIX) at Investopedia