The Linear Regression Indicator (LRI) is a stock market indicator. It’s value each day is the same as a Linear Regression Trendline (LRT). The LRI is calculated using the "least squares method." I would like to know the formula to calculate the LRI in Microsoft Excel if you could assist me.

I am uncertain how my stock charting package calculates this value, but here are some clues. For the SPY, which generally tracks the value of the S&P 500 stock index, the LRI values at the end of the trading day today were LRI(1 day)=0; LRI(2 day)=128.42; LRI(3day)=128.51. The value for LRI(2 day) is simply the closing price of the SPY for today, which was 128.42. I’m really interested in how they calculate LRI(3day), and am seeking an explanation as to why LRI(1) is 0 and LRI(2) is today’s closing price.

I’m not sure whether they use the Open, High, Low and Close for each day, or just the Close or some combo. Here are those values for the last few days: (See Additional Details)
8/3: Open=127.33; High=128.55; Low=127.15; Close=128.42. 8/2: Open=127.58; High=128.46; Low=127.55; Close=128.08. 8/1: Open=127.34; High=127.38; Low=126.63; Close=127.22. 7/31: Open=127.66; High=127.96; Low=127.46; Close=127.85

Trading indicators are best used along with money management and good risk control, using trading indicators alone will not enable you to be a successful trader, the market is just too random and unless risk is controlled over time your account will slowly get wiped out, regardless how good a “trader” you think you are.