interpolation in excel

  • Thread starter Thread starter Guest
  • Start date Start date
G

Guest

I want to use an interpolation table in excel. When I type in the value, I
want excel to look up the closest two values in the table and calculate the
corresponding value.
 
One way to try
(for a one way interpolation)

Suppose you have the reference table
below in A1:B3

X Y
100 1.5
200 2.8
300 4.5

If you earmark say,
cell D1 for input of X values

then you could put in E1:

=IF(ISNA(MATCH(D1,A1:A3,0)),FORECAST(D1,B1:B3,A1:A3),INDEX(B1:B3,MATCH(D1,A1
:A3,0)))

E1 will return the exact Y value from the reference table
if D1 contains an X value which matches (viz.: 100, 200, 300)

If D1 contains unmatched X values, say: 150,
E1 will return the interpolated value of: 2.183

Adapt to suit
 
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