With the following data set, what is the best way to interpolate the data for each time.

Time    X    Y
0      10    15
24     28    17
49     9     14
  • $\begingroup$ Best way in what sense? There are different methods and each has its own dis/advantages. $\endgroup$ – Gigili Aug 1 '12 at 8:51
  • $\begingroup$ Now I think about it more, I guess just a linear straight line fit is best for my usage. As I know my objects position at 0 and at 24, and need to estimate as close as possible where it is at any other time. in this instance it is a cube structure rotating slightly off-axis. $\endgroup$ – davivid Aug 1 '12 at 9:03

You can use Newton's divided differences interpolation polynomial which is easy to use and if you add a new point to the set, you don't have to calculate everything again.

So you'll have a table with four columns, $x_i, y_i$ and divided differences where:

$$f\left[x_0,x_1,\dots, x_n\right]=\dfrac{f\left[x_0,x_1,\dots, x_{n-1}\right]-f\left[x_1,\dots, x_n\right]}{x_0-x_n}$$

Then, for example, you have:

$x_0=10, y_0=15, x_1=28,y_1=17$: $$f[x_0,x_1]=\dfrac{y_0-y_1}{x_0-x_1}=\dfrac{15-17}{10-28}=0.11$$



Thus, the interpolating polynomial is:


And it's easy to take it from here.


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