non-linear interpolation
Hey. I have a question: how can I interpolate a value from the data I have.
for example: I have
x:1,2,3,4,5
y:1,4,9,16,25
thats not linear (thats not my actual data) and I want to know how to input a certain value in that range (x or y, because I actually want a y value) and have excel tell me the other value:
e.g.
y=5,65
x=?
but I dont want to use a trendline to have an aproximate equation. all I want is the value.
PS. I dont use excel so often, Im far from being an expert so I kindly ask for any answer to be very clear for someone like me,
thank you
Thanks a lot, thats exactly
Thanks a lot, thats exactly what I needed
RE: Interpolation
Hello,
I'm not sure that I understand you correct what you mean with "non-linear interpolation". But my guessing, base on your explanation, is that you need to use the FORCAST function, which in its general form not return the most precise result. But with some rectification, which I found in the web, it work fine. Here's an example base on your x and y values:
In cell E2 enter this formula:
= FORECAST(D2, OFFSET(B2:B6, MATCH(D2, A2:A6, 1) - 1, 0, 2), OFFSET(A2:A6, MATCH(D2, A2:A6, 1) - 1, 0, 2))
and in cell E5 enter this:
= FORECAST(D5, OFFSET(A2:A6, MATCH(D5, B2:B6, 1) - 1, 0, 2), OFFSET(B2:B6, MATCH(D5, B2:B6, 1) - 1, 0, 2))
This method have one shortcoming (one that I notice...) - it work only for values in known range. In your example, you can get y only for x >= 1 and < 5, and get x only for y >= 1 and < 25.
Finally, if this is not what you need there is another interpolation functions in excel, such as TREND, GROWTH, LINEST, LOGEST, which you can examine.
Best regards.