Forum Discussion
linear function
What is the formula for if x=5 y=1 if x=10 y=3 if x=15 y=5 if x=12,5 what is the value of y
(resubmitted to correct critical typo)
At the risk of doing your class or exam assignment for you, use LINEST to determine the coefficients of the linear approximation est y = m*x + b.
Formulas:
F3:G5: =LINEST(B3:B5, A3:A5, TRUE, TRUE)
C3: =A3*$F$3 + $B$3
Select F3:G5 and type the formula. In some versions of Excel, we must commit by pressing ctrl+shift+Enter instead of just Enter.
In this case, the linear "approximation" is an exact fit. This is indicated by r^2 = 1 in F5.
PS.... In general, it is unwise to use LINEST results blindly. The first step should be to use an XY Scatter chart to visually inspect the relationship between x and y. You can even create a (linear) trendline to determine the fit.