Questions tagged [fitting]

Questions on the use of Mathematica to construct models for approximating empirical data.

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What does the following error message mean, in the context of NonlinearModelFit?

I am deliberately not including data or a model for this question, as I want a more general answer so that I may be able to trouble shoot this myself in the future. When performing a fit, usually a ...
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1answer
48 views

Regression to fit data with an integral equation

I have a set data and I know that this data are best fitted by the following equation, assuming that f($\tau$) is a log normal distribution and $M_{eq}$ = 1.5: $M(t,\tau)= M_{eq} \int (1-e^{-t/\tau}) ...
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+100

What are the most reliable test of goodness of fit in Mathematica

I realise this is possibly a VERY open ended question, and potentially has answers dotted around e.g. here . What are the most robust methods of testing the result of ...
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3answers
50 views

Fitting a function, a (x - 1)^b, to a given set of data

I have some data: ...
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1answer
37 views

Problems with NonlinearModelFit: “..is not a real number at ” [closed]

I am a newcomer to Mathematica. Basically I just want to fit the data shown below (ArrayFVel). Unfortunately, the model contains rather complicated integral that ...
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1answer
179 views

What is the best way to use errors in mathematica M12?

Since ErrorListPlot has been superseded by new functionality in ListPlot for Mathematica 12.0, what is the best way to handle ...
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1answer
42 views

Combining fitted parameters to make a variable and telling me the error in it

I've fit my set of data to a function of the form: $a*\cos(2\pi t)+b*\sin(2\pi t)+c*\cos(4\pi t)+d*\sin(4\pi t)+e$ with a nonlinear model fit. The parameters $a,b,c,d,e$ have errors in it that ...
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42 views

How can you set the fit tolerance in `NonlinearModelFit`?

In NonlinearModelFit how can you set the tolerances of where the fitting terminates. I know you can set MaxIterations but how ...
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1answer
71 views

Nonlinear fitting does not perform appropriately

I have a list as below one: mustbefitted={{0., 1.}, {4.4, 0.982211}, {8.9, 0.961575}, {13.3, 0.942571}, {17.8, 0.923857}, {22.2, 0.906203}, {25.1, 0.046994}}; I ...
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1answer
60 views

Fitting data with NIntegration related function

I am trying to fit experimental data with data file given below function, but I am not able to find the best fit. Constant value is A=6.26 and ...
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1answer
130 views

Assign Error bars for y-intercept

I have some data (x,y) with error bars in y direction: ...
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0answers
26 views

No progress on validation NN training set

So in short my issue is that I'am training a neural network and while the training loss reduces over time, the loss of validation set remains constant. The progress of training looks like this: I am ...
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1answer
56 views

Obtain reduced chi-squared for fit

Dear Colleagues, I have performed a fit according to the code below. The last step is to obtain the value for the reduced chi-squared for the goodness of fit. Does mathematica have a ...
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1answer
57 views

How to fit data with superposition of CDFs?

With the help of @JimB, I could fit some experimental data with a CDF using NonLinearFitModel. The set of data is the following: ...
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2answers
108 views

Fitting two-dimensional data

For this question, I cannot use random sample data. So the actual data can be found here. The data file contains three columns, where the first two are the coordinates $(x,y)$, while the third is the ...
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0answers
40 views

Fitting data points with a function obtained by ParametricNDSolve+Integrate

My question concerns fitting data points to a function that is a solution of a set of parametric differential equations, then integrated over time. More specifically, I have these parametric ...
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2answers
80 views

Getting error General::munfl from NonlinearModelFit [duplicate]

I am trying to fit data to a sum of Gaussians. This data is found in a file called lpeff.txt. So I write the following code: ...
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2answers
52 views

How to find the best quadratic fit for a set of data?

I'm trying to find a degree-2 polynomial fit with x-intercepts of x=0 and x=1 for the below set of data: ...
34
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1answer
1k views

How to fit a linear model in the Bayesian way in Mathematica?

Basically, I'm looking for the Bayesian equivalent of LinearModelFit. As of the moment of writing, Mathematica has no real (documented) built-in functionality for ...
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0answers
42 views

Best Way For Estimating Parameters Of Hidden Markov Process

Parameter estimation is not stable. First, make a model. ...
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1answer
44 views

Using NonlinearModelFit function with polynomial I have defined

I have a data set that I wish to write a loop for to fit polynomials to. I want to be able to type in the max order polynomial I want it to calculate the fit for and have it solve each along the way. ...
3
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1answer
68 views

Choosing the best fit from given plots

I have some data: x={1,2,3,4,5,6,7,8,9,10} y={3.05,21.05,69.05,162.05,315.05,543.05,861.05,1284.05,1827.05,2505.05} That I plot with ...
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1answer
75 views

Fitting tail of distribution to Generalized Pareto Distribution

Hello, I have a problem in Mathematica and I don’t know if you could help me. I’m trying to compare the “performance” of a Laplace distribution and a Generalized Pareto Distribution (GPD) for the tail ...
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1answer
53 views

Put error bars in a plot from a non-linear fit together with confidence level

I want to ask you a problem that I have. I make a non linear fit with some data, and I want to know how can I put the error bars in the plot together with the confidence level of the fit that I ...
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2answers
54 views

FindDistributionParamters vs. NonlinearModelFit for NormalDistribution

I have the following data: dat["Sag"] ={1.277, 1.913, 1.48, 1.472, 1.787, 1.736, 1.896, 1.715, 1.131} I want to fit a normal Distribution to it and get the ...
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1answer
46 views

Partial and semipartial correlation

I am interested to know if there are built-in Mathematica functions that performs partial and semipartial computations. If not, what would be a simple and efficient way to compute them from the ...
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1answer
110 views

Fitting a mixture of two normal distributions for a data set?

EDIT: Raw data can be found here: https://gist.github.com/Kagaratsch/65a931d8d78fcdd81f7e346429a02afd Consider the following binned example data: ...
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1answer
65 views

Fitting nonlinear function does not converge but looks close to best fit

I'm having trouble fitting this transition temperature equation to my data. Physically speaking, the intensity should flatten out for T>Tc, which seems to be the biggest problem here. The equation I'...
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1answer
73 views

Getting errors from ParametricNDSolveValue

I am a newcomer to Mathematica (use ver 9.0). I just want to fit the experimental data to a system of odes' by using NonlinearModelFit. The data, contains time in the first column and product ...
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0answers
82 views

Problem with fitting

So I have a very simple question related to a simple topic, but also directly related to a fitting problem. I see that my question is related to this question but I don't manage to make the bridge ...
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1answer
70 views

Goodness of fit : how to perform weighted Pearson test (or equivalent)?

I wish to perform goodness of fit. Currently I use NonLinearModelFit : ...
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1answer
57 views

Finding a fit with a specific mean squared error

I have a fit a data set to the following equation ...
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2answers
92 views

FindFit or Integration Making Use of NumericQ Not Converging

Hello Mathematica Users, I'm using ?NumericQ to solve an integral numerically and then fit the data to give me values for certain parameters. The integrals involved appear in: $$ \alpha = \frac{...
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2answers
164 views

Dynamic number of parameter fits in Mathematica

I am trying to learn if in Mathematica one can perform fits of analytic functions that are expanded and written as power series. In particular, we can consider the following generic form: $$ f(B,x) = ...
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1answer
111 views

Why doesn't Mathematica completely draw the fit?

I have a question, and I really need your help, because I think I'm not understanding the reason... I have a potential model.. F[x_] := k x^n for the next ...
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0answers
44 views

Fitting a Curie-Weiss law function with a diverging point to a data

I would like to fit a function to some experimental data such that the extracted value of Curie temperature (Tc) describes the temperature at which the response flattens out to a constant value. ...
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1answer
56 views

How to fit a list of points to a certain form given error bands?

I am trying to fit a list of points to the form F[0]/(1 - a*q^2 + b*q^4), where F[0] is the value at zero of a function, which ...
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0answers
63 views

Why does ListSurfacePlot3D yield a different surface fit than using Python code for best-fit quadratic curve (2nd-order)?

Using the same data, I obtain different surface fits on Mathematica (using ListSurfacePlot3D) and Python (using a code for best-fit quadratic curve (2nd-order)). Here's my code on Mathematica: ...
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1answer
42 views

How to extract parameters from fitted model for ListSurfacePlot3D?

I would like to obtain the parameters used by Mathematica to create this surface fit of 3d data: ...
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0answers
47 views

BSpline vs natural spline [closed]

The BSpline in mathematica is defined mathematically here. These BSplines constitute basis for any Spline. But how do I define natural splines in mathematica, i.e. splines that are linear left of the ...
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3answers
109 views

Tangent point coordinates when the curve is a set of points

I want to find the coordinates of the tangent point between a convex curve and a line that passes from a point with known coordinates (0,b) ("efficient portfolio" ...
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2answers
57 views

Accessing nonlinear fit coefficients

I have performed a nonlinear fit onto a set of data according to the form $a+b\cos(2\pi x)+c\sin(2\pi x)+d\cos(4\pi x)+e\sin(4\pi x)$. How do I access the best fit parameters $a,b,c,d,e$, store them ...
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1answer
41 views

Why UnitCovert doesn't work with Fit?

I need to find the Hubble constant (Ho) in light years, from some data, the exercise tells me that the constant of the hubble is the slope of the line. data: r1 is in MegaParsecs. ...
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1answer
89 views

NonlinearModelFit returning imaginary numbers after fitting real data

I am getting problems when I try to use NonlinearModelFit to fit a squareroot-like function to a set of real data points. Here is the function: \begin{equation} \...
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2answers
187 views

NonlinearModelFit when the fitting function produces a discrete list of values?

Short Version: I have a parameterized function (the model) that returns a list of values. I have data that I want to fit this model to, optimizing those parameters, where the list position in the data ...
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2answers
136 views

How to find fit for this plot?

I have been trying to find an expression that properly models the following plot in Mathematica v9.0: I have tried modelling it as odd-degree polynomials using Fit,...
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1answer
192 views

Fitting multiple data with model and NDSolve with different initial conditions, and other shared parameters

I know that there are already questions about fitting multiple datasets and about NDSolve and about shared and non shared parameters, but I tried to apply them and some things are still not clear. ...
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1answer
53 views

Fitting system of differential rate equations to data

I am trying to fit a set of differential equations to experimental data, without luck so far. These are the data: ...
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27 views

Fitting 2 curves nonlinearmodelfit

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2answers
140 views

How to do an exponential fit for this data?

Whenever I try to use FindFit or NonlinearModelFit for the data (shown below), I keep getting the following error thrown at me: ...