Hello,

I have a data set organized in a ROOT file of a 4 dimensional function (F(x,y,z,t) = c) for a span of values for x, y, z, and t.

I want to interpolate the function for values not in the data set and am looking for options to pursue. I have tried a multi-linear approach but run into an issue when trying to find the ‘nearest-neighbors’ of the point I’m trying to interpolate, there is just a mess of for-loops trying to search the tree branch for the right values that it takes too long. **Question: is there an easier way to search root files for entry values?**

Also, there is the ROOT::Math::Interpolator class, but it seems that this can only be used for 1D functions (F(x) = y). **Question: are there any higher-dimension options for interpolation within ROOT?**

I’ve tried using TMVA and have a working code, but would rather make a calculation that I can understand, but if there is no easier option then this will be okay.

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*ROOT Version:* Not Provided

*Platform:* Not Provided

*Compiler:* Not Provided