--[[
--Formula :
--Trend Line Equation(y) = a + bx

--Where,
--      Slope(b) = (NSXY - (SX)(SY)) / (NSX2 - (SX)2)
--      Intercept(a) = (SY - b(SX)) / N

--This tool will help you to dynamically calculate the trendline chart online. Trend line --is also referred as Dutch Line or Line of Best Fit.
--]]--

-- http://easycalculation.com/statistics/trend-line.php
-- http://www.easycalculation.com/statistics/learn-regression.php
-- http://easycalculation.com/statistics/trend-line.php

function regression()
	print ("Enter number of points:")
	n=io.read()
	sum_x=0
	sum_y=0
	sum_xx=0
	sum_xy=0
	for i=1,n do
		-- print ("For point",i)
		-- print ("Enter x:")
		x=i
		print ("Enter y:")
		y=io.read()
		sum_x=sum_x+x
		sum_y=sum_y+y
		xx=math.pow(x,2)
		sum_xx=sum_xx+xx
		xy=x*y
		sum_xy=sum_xy+xy
	end

	--Calculating the coefficients
	a=(-sum_x*sum_xy+sum_xx*sum_y)/(n*sum_xx-sum_x*sum_x)
	b=(-sum_x*sum_y+n*sum_xy)/(n*sum_xx-sum_x*sum_x)

	print ("The required straight line is Y=",b,"X+(",a,")")
end

regression()