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Asked: 2026-06-07T09:16:15+00:00

I am trying to run NonlinearModelFit in mathematica on some data for a project.

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I am trying to run NonlinearModelFit in mathematica on some data for a project. It is a fairly complicated model having 9 coefficients, and 5 independent variables. I created the data the way that the model needs, and I think I called the function correctly.
Here is a sample of the data:

{{16.5892, 0.631, 1.7707, 1258.21, 580.271, 14.02}, {16.2855, 0.813, 
1.76756, 2098.41, 745.624, 13.59}, {16.036, 0.58, 1.77311, 846.994, 718.092, 13.41}}

Of course the total amount of data is about 30 data sets for the function to use.
Here is my function call:

nlm = NonlinearModelFit[data, a + c*b + d*bminv + e*M + f*bminv*M + g*x + h*x^2 + i*y + j*y^2,
{a, c, d, e, f, g, h, i, j}, {b, bminv, M, x, y}];

I think that this should work, but I get a really weird output:

FittedModel[38592.8+0.811612b+<<9>>+3.06099*10^-7*y^2]^3

The numbers for this model might be right, but I do not understand the part with <<9>>, and even more so I do not understand how the FittedModel function, which is what NonlinearModelFit always returns, is cubed.

Besides the weirdness of the output, it is also an unusuable output, I have tried functions that should work with FittedModel objects, and none of them work.

If anybody has some advice as to what the output means, how to fix it, or if I am simply doing something wrong with my function call or data it would be much appreciated.

Thanks.

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1 Answer

  1. Editorial Team

    It seems to work and I don’t get the ^3 :

    data = {{16.5892, 0.631, 1.7707, 1258.21, 580.271, 14.02}, {16.2855, 0.813, 1.76756, 2098.41, 745.624, 13.59}, {16.036, 0.58, 1.77311, 846.994, 718.092, 13.41}}

nlm = NonlinearModelFit[data, a + c*b + d*bminv + e*M + f*bminv*M + g*x + h*x^2 + i*y + j*y^2, {a, c, d, e, f, g, h, i, j}, {b, bminv, M, x, y}] ;

nlm[Sequence @@ Most[#]] & /@ data - data[[All, -1]]

(* {-1.77636*10^-15, 0., -3.55271*10^-15} *)
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