In days past I wrote an Excel subroutine for a Weight & Balance / Performance spreadsheet I wrote for when I was flying a Metro III doing on call cargo. I had this installed on a Palm III that I could use to assist in calculating the performance stuff while loading the aircraft
Basically all you need to do is set up your charted data into the spreadsheet formatted so that you can do a VLOOKUP on the two values that envelope your desired value. Then all that is necessary is a ratio calculation. All that means is taking the "spread" between your known values and seeing what percentage of those values your desired value represents. Piece of cake.
Just remember that many times even with the tables that you are looking at values that are represented may not be linear, they could be logarithimic, and this could be representative of what I refer to as fractionally factorical (such as 10 to the .23 power versus a whole number - wrap your head around that one!) or it could be something else entirely. This is all well above my very basic mathematical understanding. Mathematics is something I wish I knew more about.
The interpolation routine I referred to should be sufficent to your needs. It all ties into the old saying "Measured With A Micrometer, Cut With An Ax!"
If pushed I could try to find the spreadsheet but I don't have a lot of free time right now.
Playing with Excel is fun and there is a lot that you can do with it. Give it a try!
Last edited by FearlessFreep; 22nd Apr 2006 at 15:39.