Questions tagged [fitting]

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

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Solving one equation, then inputting the values into another for NonlinearModelFit

Considering the equation a*x^3 + a*x^2 + x + b == 0 I'm looking to find the best value for a and ...
650 views

How to define a pure function with a Module?

I was not able to use a self defined (using Module and For loops) piecewise function to fit data. It seems that the problem is that I have to define a pure function. I would like to learn how to ...
5k views

Using NonlinearModelFit to fit data with errors

Assume we have some data of measurements SeedRandom; data = Table[{i,2*(1 + 5*RandomReal[])*Exp[-0.01*(1 + RandomReal[])*i]}, {i, {0, 100, 200, 400, 700}}]; ...
560 views

Unexpected behavior of confidence bands for data presenting two regions with uneven noise

Let's generate some noisy data with uneven noise. ...
429 views

Performance in parameter estimation from ParametricNDSolve using varied initial conditions [duplicate]

I have 250 data points from a timecourse exeriment in a list, with columns specifying (1) time, (2-4) initial conditions, (5) absorbance reading. I want to fit 4 parameters (k1, k2, k3, k4) in a DAE ...
893 views

How to adjust parameters to experimental data on a NDSolve problem

I have 2 differential equations with 2 variables, x and y,which are a function of t and I have the parameters k1, k2 y k3. ...
2k views

Remove linear trend from data

I have a large data set with 150k lines and two data columns. I noticed that there is a linear trend, which I want to remove. So, I do the following: First, fit with a linear model: ...
1k views

Linear regression in a chosen range of points

Hi I'm absolutely newbie in Mathematica and have following problem: My list looks like {{50, 0.75}, {51, 0.76}, ..., and I want to choose a range out of my x-...
148 views

Putting a matrix inside function

I want to fit a function to some data and inside the function there's a list here's my data ...
994 views

Using perpendicular offsets in FindFit

I want to use perpendicular offsets in the built-in FindFit function. Are there any possible ways or do I have to code everything by myself?
2k views

Does LinearModelFit perform an ordinary linear regression (least squares)?

Does LinearModelFit give an ordinary linear regression? I see lots of options, but nothing like "least squares" or OLR.
3k views

Fit line similar to power of trendline in Excel

Is there a way to fit a line similar to power trendline in Excel? Something in this fashion: Fit[data, {1, x, x^(-n)}, x] ...
253 views

How can I nicely overlay fits for multiple arrays with ListPlot or ListLogPlot?

I'm plotting multiple lists with ListPlot[] or ListLogPlot[]: ListLogPlot[{ListA, ListB, ListC, ListD, ListE}, PlotRange -> {{0, 100}, Automatic}] I also have ...
310 views

FindFit: Fit that is always lower - Change of Norm?

I am trying to find a fitting function for a multidimensional set of data. I will have to find a fitting function that is always lower (conservative) than the data fitted. The easiest way is to look ...
3k views

Smoothing/Averaging 2D Vector Fields

I have a list of 2D vectors defined by {{x,y},{u,v}} and would like to smooth or average the vectors. For example here are 2 vector fields, the second has noise ...
526 views

Using a user defined NormFunction in FindFit or NDSolve

I would like to use a different norm instead of the 2-norm in FindFit (Mathematica 9). For example, instead of using \sqrt{\sum (x_{\mathrm{model}} - x_{\mathrm{...
2k views

How can I consistently get a good logistic regression fit?

I'm executing the command NonlinearModelFit[data, c/(1 + a Exp[-b x]), {a, b, c}, x] with the data being ...
945 views

Is it possible to marginalize one or several parameters obtained from fitting procedure?

Statistical model analysis package has a few fitting functions. Their arguments are data points, fitting model and parameters in the fit. The result is a set of best values for parameters, which ...
1k views

Method used by FindFit

Using FindFit, Mathematica selects an optimal algorithm when Automatic is selected. I'd like to know the name of the method ...
1k views

How to get confidence bands of parameters from a fitting procedure?

I have done fitting of data points with a given model that has two parameters (A and B), using NonlinearModelFit. The result of the fit is the maximum of the ...
2k views

Multinomial logistic regression

Has anyone done multinomial logistic regression in Mathematica? The binomial case is essentially done on the LogitModelFit documentation page and works fine. I am ...
5k views

Methods for NonlinearModelFit

I am using NonlinearModelFit for a thesis project. I get quite different results if I change the Method to LevenbergMarquardt or QuasiNewton or ConjugateGradient ...
1k views

Problem using NDSolve

This might be some simple mistake, but I am running out of ideas. I am trying to fit an ODE system to some data. This error keeps appearing NDSolve::nlnum: "The function value {0.299812 - 0....
512 views

Specify a constraint on an interval under FindMinimum

I have an interpolated function that looks like this: $\hskip1.2in$ and, based on extreme and critical points, I want to use a polynomial to approximate the function. The points in question are: <...
3k views

FindFit: getting confidence intervals for the returned parameters

I'm using FindFit[] to fit a function to some experimental data. I'd like to know what error bars are on the fitted parameters. Scipy's ...
315 views