Interpolated data look-up in xls sheet using 4 variables. How to do this?

Hi All,

Attached is an xls file from which I am trying to get automated output based on input of 4 variables.


input:

1. Brake on speed
2. Weight
3. Temperature
4. Pressure Altitude

Output:
1. Reference brake energy.

Input values could be values in between the table values; e.g.
1. Brake on speed: 150 KIAS
2. Weight: 250 TONS
3. Temperature: 25 DEGREES C
4. Pressure Altitude: 2000 FT

should return the output of 56.24

I need some advise on how to do this. I was thinking of making several graphs with trend lines and deriving formulas, but maybe there is an easier way...
Any help would be greatly appreaciated. Thanks in advance!

Hi John,

Understood. The file was generated by a PDF to XLS converter, that's why it contained strings.
I just modified it so that all data is usable. See attachment. Thanks.

See attached columns AA:AB for standard INDEX/MATCH calculations

Result does not agree with yours: I suspect you did some extrapolation as 56.24 does not exist in the table.

We are going in the right direction.

But what is required is 4 times a double interpolation.
The 16 values that need to be interpolated are highlighted in the attachemnt.
Each area of 4 values needs a temperature interpolation (so 50% up vertically from the lower valua (25 lies between 20 and 30), and 20% up horizontally from the lower value (2000 feet is 20% up between 0 and 5000 feet).
The average of the 4 results is the final result. I am getting 54,99 now...

Seems to be quite a difficult task to make this work.

It is late now but I don't understand why you are extrapolating to 160.

You need to explain your extrapolation logic.

Signing off now!

The sample 4 values that were given in my example do not match exactly with any cell value.

1. Brake on speed: 150 KIAS -> This value needs to interpolated between 140 and 160 KIAS
2. Weight: 250 TONS -> This value needs to interpolated between 240 and 260 TONS
3. Temperature: 25 DEGREES C -> This value needs to be interpolated between 20 and 25 DEGREES C
4. Pressure Altitude: 2000 FT -> This value needs to be interpolated between 0 and 5.000 FEET.

This leaves us with 4 sets of 4 figures that need to be interpolated.
The average of the 4 results is the correct outcome.

Managed to solve the interpolation issue.

Took John's solution as basis and assigned the cell for interpolation by shifting the index results by +6 vertically and +3 horzontally.
Still need to makes sure interpolation is not done outside the index matrix. I will do this by restricting the input values...

Thanks again John!