Thread: Real-Time Curve Interpolation Excel 2007

Hi,

I am using Excel 2007 and I would like to interpolate values.

The Xs and Ys will be changing real-time in excel. So the interpolated values need to be updated in real-time as well.

Attached is an example of my data. The values in Column A and B will be changing real-time. Column E values are static and do not change, they will only change if I decide to enter in different values of X to interpolate. The interpolated values in column F will be dynamic and change since columns A and B are changing.


Thanks

example.xlsx

Hi,
You will see attached the result of the interpolation
The interpolation from the actual data points is difficult due to the fact that the interpolated extreme points are outside of the range
First extract the trend curve from the F(x) Actual data chart, apply the formula to interpolate
Very bad result for value outside of the negative axis on the F(x) Trend chart
Download the add-ins XlXtrfun from XlXtrFun™ Extra Functions for Microsoft Excel
The result on F(x) XlXtrfun chart looks better
I am sure than a guru will find a better solution without add-ins
Hope this will helps
Best regards

Try this.... let me know how it works for you/.

Here is the formula I used, it can be adjusted to meet your needs:

=(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1)*E3^5)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,2)*E3^4)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,3)*E3^3)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,4)*E3^2)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,5)*E3)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,6))

Good luck,

Mark

Originally Posted by jpr73

Hi,
You will see attached the result of the interpolation
The interpolation from the actual data points is difficult due to the fact that the interpolated extreme points are outside of the range
First extract the trend curve from the F(x) Actual data chart, apply the formula to interpolate
Very bad result for value outside of the negative axis on the F(x) Trend chart
Download the add-ins XlXtrfun from XlXtrFun™ Extra Functions for Microsoft Excel
The result on F(x) XlXtrfun chart looks better
I am sure than a guru will find a better solution without add-ins
Hope this will helps
Best regards

thanks, the add-in works great

thanks, formula is a bit long but still works

Originally Posted by mgaworecki

Try this.... let me know how it works for you/.

Here is the formula I used, it can be adjusted to meet your needs:

=(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1)*E3^5)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,2)*E3^4)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,3)*E3^3)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,4)*E3^2)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,5)*E3)+(INDEX(LINEST($B$3:$B$43,$A$3:$A$43^{1,2,3,4,5}),1,6))

Good luck,

Mark

thanks, formula is a bit long but still works