This ProBuilder code snippet demonstrates how to calculate and visualize the starting point of a linear regression channel. The code calculates the linear regression based on a specified lookback period and draws the regression line and its starting point on a chart.

//PRC_Std and Ste LinRegChannel | indicator
//Standard Deviation and Standard Error
//Linear Regression Channel
//12.03.2019
//Nicolas @ www.prorealcode.com
//Sharing ProRealTime knowledge

defparam drawonlastbaronly=true
defparam calculateonlastbars=1000

// --- settings
lookback= 20 //channel period
// --- end of settings

sumx = 0
sumy = 0
sumxy = 0
sumx2 = 0

for cmpt = lookback downto 0 do
    tmpx = cmpt
    tmpy = close[cmpt]
    sumy = sumy+tmpy
    sumx = sumx+tmpx
    sumx2 = sumx2 + (tmpx*tmpx)
    sumxy = sumxy + (tmpy*tmpx)
next

n = lookback+1

if (sumx2 = sumx * sumx) then
    // protection to avoid infinite values
    b = sumxy - sumx * sumy
else
    b = (n * sumxy - sumx * sumy) / (n * sumx2 - sumx * sumx)
endif

a = (sumy - b * sumx) / n

drawsegment(barindex[lookback],a+b*lookback,barindex,a+b*0)
drawpoint(barindex[lookback],a+b*lookback,3) coloured("yellow")

return linearregression[lookback] coloured("red"), a+b*lookback coloured("yellow")

The code snippet above performs the following steps:

• Initialization: Sets up the environment to only draw on the last bar and calculates based on the last 1000 bars.
• Settings: Defines the lookback period, which is the number of past bars to consider for the regression calculation.
• Variable Initialization: Initializes variables to store sums of x values, y values, x*y, and x^2, which are needed for the regression calculations.
• Loop: Iterates over the past ‘lookback’ number of bars to sum up the values required for the regression formula.
• Regression Coefficients Calculation: Calculates the slope (b) and intercept (a) of the regression line. Includes a check to prevent division by zero, which could occur if all x values are the same.
• Drawing on Chart: Uses drawsegment to draw the regression line and drawpoint to highlight the starting point of the regression line in yellow.
• Output: Returns the value of the linear regression at the lookback period and the y-coordinate of the starting point of the regression line, both colored for visual distinction.

This example is useful for understanding how to implement statistical calculations and visual elements in ProBuilder to analyze financial data.