How FillSeries Calculated for numbers when select and drag the multiple cells in the Excel?

Question

I need some clarification on excel FillSeries calculation for numbers.

Actually I have selected the three cells which contains some number, then I have do the fill series by drag and fill method.

But I don't know how excel calculate and display the fillSeries for numbers.

So anyone can suggest your idea for the calculation? Excel using any formula for the FillSeries calculation?

Answer 1

Excel calculates the linear trend line. This is done by:

a = 4 x {(1 * 1) +( 2 * 2) + (3 * 4) + (4 * 5)} = 148
b = (1 + 2 + 3 + 4) x (1 + 2 + 4 + 5) = 120
c = 4 x (1^2 + 2^2 + 3^2 + 4^2) = 120
d = (1 + 2 + 3 + 4)^2 = 100

The step value = (a - b) / (c - d) = 1.4

Next you need the intercept

e = (1 + 2 + 4 + 5) = 12
f = step value x (1 + 2 + 3 + 4) = 14

The intercept = (e - f) / n = -0.5

This gives you the forumla of -0.5 + 1.4x

so for the 5th value this is -0.5 + 1.4 * 5 = 6.5

Every value after this is an addition of 1.4