How to use Interpolation to fill in missing data

Question

I have a bit of data that looks like this:

data = {79., 79.1, 78.3, 78.6, 79., 77.2, 79.3, 79.3, "", "", 79.3, 76.6, \
79.3, 79.8, 78.4, 79., 78.4, 78.4, 79.4, 79.5, 79.4, 79.3, 79.2, \
79.2, 79.3, 79.6, "", 79.2, 79.3, 79., 79.1, 79.2}

I'm looking to do Linear Interpolation to fill in the missing data. The Interpolation functions with InterpolationOrder->1 seems to be just what I am looking for. But I can't figure out how to feed the data to the Interpolation function in order to get a a sensible result.

Answer 1

You have to provide the values of independent variable. Assuming that the points correspond to equidistant values of an independent variable, you can do this, for example:

int = 
 Interpolation[
   Select[Transpose[{Range[Length[data]], data}], NumericQ[Last[#]] &],
   InterpolationOrder -> 1
 ]

Of course, you may wish to scale the independent variable here in some way.