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Wolfram Language Numerical Computation

How to subtract interpolating functions

Charles Rackson

Posted 10 years ago

Hi, I've generated two, 2-dimensional interpolating functions nu1 and nu2, and I'd like to subtract them to generate a third function. This doesn't work: In[123]:= nudifference = nu1 - nu2 Out[123]= InterpolatingFunction[{{-0.5, 0.5}, {0., 0.866025}}, <>] - InterpolatingFunction[{{-0.5, 0.5}, {0., 0.866025}}, <>] Does anyone know how to make a function that's the difference of two interpolation functions? Thanks!

POSTED BY: Charles Rackson

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Marco Thiel

Marco Thiel, University of Aberdeen - Dept. of Physics/Mathematics

Posted 10 years ago

Hi, does this work for you? (Generate data) x = RandomReal[1, {100}]; y = RandomReal[1, {100}]; (Interpolate) f = Interpolation[x]; g = Interpolation[y]; (Define difference function) h = f[#] - g[#] & (Evaluate h) h[5] (Out:= -0.193709) (Plot h) Plot[h[x],{x,1,100}] If you are careful about it, you can even differentiate it (I used InterpolationOrder-> 2 for this): Plot[h'[b], {b, 1, 100}] Cheers, Marco

Hi,

does this work for you?

(*Generate data*)
x = RandomReal[1, {100}]; y = RandomReal[1, {100}];

(*Interpolate*)
f = Interpolation[x]; g = Interpolation[y];

(*Define difference function*)
h = f[#] - g[#] &

(*Evaluate h*)
h[5]
(*Out:= -0.193709*)

(*Plot h*)

Plot[h[x],{x,1,100}]

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