## Ergodic True Strength Index

Ergodic True Strength Index (ETSI) was authored by William Blau. The ETSI uses price and previous price, with differences and absolute differences, in a series of exponential moving averages (EMA’s) to arrive at its ergodic oscillator value. A signal line which is an EMA of itself is also given. The user may alter the input (close), method (EMA) and period lengths. This indicator’s definition is further expressed in the condensed code given in the calculation below.

### How To Trade Using Ergodic True Strength Index

Although a signal line is plotted, no trading signals are calculated for this indicator.

### How To Access in MotiveWave

Go to the top menu, choose Study>William Blau>Ergodic True Strength Index

or go to the top menu, choose Add Study, start typing in this study name until you see it appear in the list, click on the study name, click OK.

Important Disclaimer: The information provided on this page is strictly for informational purposes and is not to be construed as advice or solicitation to buy or sell any security. Please see our Risk Disclosure and Performance Disclaimer Statement.

### Calculation

//input = price, user defined, default is close
//period1 = user input, default is 4
//period2 = user input, default is 8
//period3 = user input, default is 6
//sPeriod = user input, default is 3
//method = moving average (ma), user defined, default is EMA
//prev = previous, index = current bar number

```etsi = 0;
prevP = price[index-1];
priceD = price - prevP;
absPriceD = Math.abs(price - prevP);
ma1 = ma(method, index, period1, priceD);
aMa1 = ma(method, index, period1, absPriceD);
ma2 = ma(method, index, period2, ma1);
aMa2 = ma(method, index, period2, ama1);
ma3 = ma(method, index, period3, ma2);
aMa3 = ma(method, index, period3, ama2);
Plot1: etsi = (100 * ma3) / aMa3;
Plot2: sig = ma(method, index, sPeriod, etsi);```