Interpolation between multiple data values: [SOLVED]

[GrahamF]

Please help - I am trying to interpolate table values for multiple numbers - I have tried forecast and trend and neither seem to supply the correct values:


EG: If I had to interpolate between the given data - I would work out the difference between(92.4-91.2)=1.2, and (45-40)=5 then divide 1.2/5=0.24 giving the change for every unit. This I would add to the original ie: 91.2 + 0.24 = 91.44. This I would continue until I have interpolated across the entire range. This however is cumbersome and a lengthy process - ie: =AE71+(($AI71-$AD71)/5)


45 91.2

44

43

42

41

40 92.4

 

[GrahamF]

This is the interpolated answers for the above query that I need help with - Trend/ Forecast does not work -.....

45 91.2

44 91.44

43 91.68

42 91.92

41 92.16

40 92.4


The below table I have to interpolate between all temperatures in 1°C intervals, and Heights in 100ft intervals (they are in 1000's of ft)


°C S.L. 5 10 15 20 25 30 35 40 45

45 91.2 91.6 92.1

40 92.4 92.8 93.1

35 93.5 93.8 94.1 94.4

30 94.4 94.7 94.9 95.1

25 95.3 95.5 95.6 95.7 95.6

20 95.6 96.1 96.2 96.3 96.2

15 94.8 96.6 96.7 96.7 96.6 96.6

10 93.9 97.1 97.1 97.1 97 97 96.6

5 93 96.5 97.4 97.4 97.3 97.3 97 96.3

0 92.2 95.7 97.6 97.6 97.5 97.5 97.3 96.6 94.7

 

[Hui]

Graham


I'd use a formula like: =TREND($B$2:$B$3,$A$2:$A$3,C14)

You can change the ranges for an offset that looks up the right pair of data but

You haven't told us why/what the columns 5 .. 45 do ?

Why do you select the first column?


Assuming you want them all here they are:

https://www.dropbox.com/s/18e1aqihcigiqpq/Forecast.xlsx


You can fix up the 0 row manually

 

[GrahamF]

Thats Awesome!!!


Works great - This table is an extract from a Learjet 35 performance manual. The 1st Column is the variable temperature and the top is the operating altitude in 1000s of feet.


We use this to calculate performance.


Thanks again