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

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2
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0answers
58 views

ANCOVA (ANalysis of COVAriance)

I have two time series of the form {time, value} I have linear fits of each set individually, and I am interested in the statistical differences between the ...
2
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0answers
51 views

Kalman filter estimation

Does anyone have any examples of the estimation of Kalman filters in Mathematica? I am new to these filters and struggling to compose the likelihood function. Some examples would be really helpful. ...
2
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2answers
122 views

RSquared: LinearModelFit vs NonlinearModelFit

I'm trying to understand the differences between LinearModelFit and NonlinearModelFit. One thing I notice is that the computation of AdjustedRSquared seems to be different, even when the model results ...
2
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0answers
53 views

Is there a way to produce a FittedModel object as the solution to a regularized regression?

I can get the Ridge or Tikhonov regression solution to Y = \[Beta].X easily enough as ...
2
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0answers
149 views

Power::infy: error using FindFit [closed]

I have a 2D data to fit (the Airy type pattern from diffraction of Gaussian beam on the circular aperture). Please see the attached picture. I was going to use a function like ...
2
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0answers
63 views

Why do EstimatedDistribution and DistributionFitTest work this way

I am fitting some time-series data to both a stable distribution and a normal distribution in order to assess the goodness of fit of each. Along the way I encountered the following confusing result. ...
2
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0answers
344 views

Speeding up Nonlinearmodelfit by constraining parameters?

I have a complicated parametric PDE that can be fitted to some data with NonlinearModelFit, but takes several hours to estimate the best values of the four free parameters. Currently, the code ...
2
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0answers
172 views

NonlinearModelFit is not giving the fit with minimum chi^2

First of all, a bit of background, I am using Mathematica to fit angular distributions of gamma rays, so I apologize for some of the serious messiness in the formulas. The data is simple I have three ...
2
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0answers
740 views

Linear regression with x and y errors

I have a question about finding a linear regression weighted with x and y errors. I found the answer provided by 0x4A4D in Estimate error on slope of linear regression given data with associated ...
2
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0answers
341 views

NonLinearModelFit with Two Dimensional List of Weights

I'm currently trying to fit Planck's law (B[λ, T]) to measurements, thereby determining Planck's constant. I have a list of triplets containing wavelength, ...
2
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0answers
774 views

ParametricNDSolveValue or NDSolve + fitting

I have been trying to find the value for the parameter kestim that yields the best fit of a model to some data points. datac has ...
2
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0answers
219 views

How to predict some constant number of values with NeuralNetworks

Example: << NeuralNetworks` data = {Sin[#]} & /@ Range[0, 4 Pi, 0.5]; learn = data[[1 ;; 15]]; Now, lets fit our neural network: ...
1
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2answers
176 views

Is it possible to monitor the sum of squared errors in a NonlinearModelFit or FindFit procedure during the process?

Since fitting procedures using NonlinearModelFit (or FindFit) sometimes take very long, I would like to monitor the sum of ...
1
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2answers
189 views

FindFit giving weird values on a logistic equation

I was trying to fit a set of data onto a logistic equation, however it ended up telling me that the initial value when $t=0$ is greater than the maximum limit, thus I am led to believe that it isn't ...
1
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1answer
1k views

How to find local minima of a multivariate function with singularity?

I am working on a logistic regression problem which requires minimizing a cost function J[{theta0, theta1, theta2}, X, y] to find the optimal value for fitting ...
1
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3answers
895 views

Why does FindFit seem to have trouble fitting exponential data?

I have 4 data points. t is in minutes, and y is radioactive counts per minute. When I input the following lines: ...
1
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2answers
1k views

Finding a best fit curve and plotting it [closed]

I have a list as shown below: m01 = {{250, 0.083121}, {200, 0.0888446}, {150, 0.0992422}, {100, 0.121567}, {50, 0.186825}} I'm new to Mathematica, and would like ...
1
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2answers
64 views

Encoding variables

I'm trying to fit a Logistic Model using LogitModelFit in Mathematica. The data I'm using contain qualitative variables that I have to encode. I've searched in ...
1
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1answer
189 views

How do I construct a non-linear model from experimental data?

I want to find a function $w=f(x,y,z)$ that fits experimentally determined values of w. For example, assume ...
1
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1answer
899 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 ...
1
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2answers
92 views

Does FindFit use symbolic differentiation?

Does FindFit use symbolic differentiation when optimizing by least squares a non-linear function?
1
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2answers
153 views

How to fit exponential function which is not converging

I performed an experiment where I measured diffusion in a lipid bilayer. I performed the measurement by fluorescently labeling some molecules in the bilayer, and the irradiating them with light ...
1
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3answers
224 views

Getting an equation of particular curve

How can I get an equation of the similar shaped curve? I've tried to get it like y = a + c x^2 + d x^3: ...
1
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2answers
329 views

Can't find a fit for Erf

I have the following numbers ...
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2answers
173 views

How to Fit experimental data with 4D ParametricNDSolve?

Let me first explain the background problem. I'm trying to solve a problem with a projectile motion in 4D such that the position vector is: $\boldsymbol{r}(t)=\boldsymbol{r}[x(t),y(t),z(t)]$ I have ...
1
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1answer
193 views

General F statistic and p value in LinearModelFit

Many statistical packages provide a "F statistic" and the corresponding p value in their output of a multiple linear regression. I don't find that in the parameters of the Mathematica function ...
1
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1answer
173 views

show fit information on plot

After performing a fit in Mathematica, I would like to show the fitted parameters in a box on the plot showing the fitted function. How would I go about achieving that? Here is a MWE: ...
1
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1answer
202 views

NonLinearFit with “complicated” integral model

I have a set of data $y_i (z_i)$ with errors $\Delta y_i$ ...
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2answers
108 views

Minimizing the maximal residual in mathematica

With this: d1 = 10; d2 = 4; mat = RandomReal[{-1, 1}, {d1, d2}]; vec = RandomReal[{-1, 1}, d1]; LeastSquares[mat, vec] ...
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2answers
97 views

How can I get a fully functional FittedModel when fitting data to a pointwise function?

When I am fitting data with a pointwise function using NonlinearModelFit, the produced FittedModel fails to calculate variances ...
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1answer
470 views

Fitting parameters of user defined function returning discrete values

So, I'm fairly new to Mathematica (apologies in advance for the noobiness), and I'm having some problems regarding fitting the parameters of a user defined function to data. I'll give a representative ...
1
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1answer
38 views

Convert Dates to values on an X axis

I have a bunch of dates and values which I put into the DateListPlot to get a graph. However I would also like to put this information into the Fit or LeastSquares to estimate what the value would be ...
1
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1answer
57 views

Wrong fit with FindFit

I have a set of data (Datax for x-axis and Datay for y-axes) to fit to a sigmoidal function (Hill type). While Origin gives me the right answer, Mathematica does not. The fit values given by Origin ...
1
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1answer
132 views

how to find curve fitting parameters without an explicit relation between x and y?

Let's say I have some experimental data (x,y) and I want to find some fitting parameters. But in my mathematical model, the fitting parameter are not in a simple equation that relates x and y. For ...
1
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1answer
98 views

Fitting an imported .txt data

I have some data in a .txt file, and I'm trying to import it to Mathematica and fit it with a function. The data is a 647x647 matrix of values. This seems like it ...
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1answer
152 views

Fitting Function with 3 parameters

I am trying to fit a function with 3 parameters however the result strongly depend on the initial values of parameters: ...
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1answer
322 views

Curve fitting data to model

Example Assumptions: ...
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1answer
303 views
1
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1answer
44 views

How can I plot more regression trend line in the same graph?

I would like to do something like the example I drawed manually: ...
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1answer
54 views

Traffic growth forecast: showing the change of linear regression

The following picture shows a changement in the trend of data. (The data used are available here). Is there any tool that can show this change of trend? Until now I managed to show even more ...
1
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1answer
105 views

FindFit::nrlnum: error with FindFit

I am trying to write a code to fit actual data of the orbit of a star with Mathematica 8. First I tried to write a code to fit a mock orbit, using the Application with differential equations (the ...
1
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2answers
191 views

How to obtain the best possibe NonlinearFit

Here is some sample data ...
1
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1answer
58 views

Why does my Dynamic NonliearModelFit keep running?

I have complex data and which I am fitting to a complex formula. In order to use NonlinearModelFit I split the formula and the data into real and imaginary parts. ...
1
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2answers
80 views

FindFit is producing a list of imaginary numbers when there is non

I am trying to find the fit of an equation to some data and mathematica thinks there is a list of imaginary values. My data is all real positive number. ...
1
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1answer
263 views

Find polynomial equation for set of 3D data

data was given in columns in the order {y, x, z}, with y dependent on x, z ...
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1answer
360 views

FindFit (Jacobian Error) [duplicate]

I, like others before me, am struggling with FindFit. So, I tried a simple example. ...
1
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1answer
173 views

Fitting data using a series of Sin and Cos

I have the following data representing the normal displacement caused by a normal load applied at the middle cross section of a cylinder: I've made the data available here. I am trying to fit ...
1
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1answer
313 views

Can ParametricNDsolve be used for coupled PDEs with 5 parameters?

I have a system of coupled PDEs with five parameters that I only know ranges for rather than explicit values, and I was wondering if I could define a parametric equation with ParametricNDSolve and ...
1
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1answer
123 views

Find Numerical Derivatives (With Errors) given some data

I have a question. Suposse I have some data with their respective errors: ...
1
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1answer
1k views

Keeping Nonlinear Model Fit Real

So I am using the NonlinearModelFit (NLM) command with a fairly simple function. There are 4 unknowns and the (x, y) points that ...