1. Chapter 2 Excel Fundamentals
Linear Interpolation
Chapter 2 Excel Fundamentals
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2. Population Example The population data of a town is given in the table
We maywant to estimate the population in any year: 1995, 1983, etc.
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3. Linear Interpolation
With linear interpolation, we assume that our data varies linearly between data points:
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4. Formula for Linear Interpolation
Point x falls between x1 and x2. The y-values corresponding to x1 and x2 are given (y1 and y2, respectively). Find the y value corresponding to x. x1 x2 y2 y1 x y
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5. Formula for Linear Interpolation
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6. Population Example y2 = 4086 y y1 = 3012 x = x1 = 1950 x2 = 1960 1956
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7. Linear Interpolation Description
(increase in x) * slope + starting y value (y1)
increase in x = x – x1
slope = (y2 – y1)/(x2 – x1)
If population = 7000 (y1) in 2000 (x1)
8000 (y2) in 2010 (x2)
Population in 2008 =
(2008 – 2000)*(8000 – 7000)/( ) +7000
8*(1000/10) 8*
7800
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