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

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2
votes
2answers
52 views

FindDistributionParameters gives an error for a mixture of user defined sinh-arcsinh distributions

I have some data (1593 values). I first binned it using the Knuth rule and fitted a function that is a linear combination of two sinh-arcsinh functions. I then ...
3
votes
1answer
170 views

ODE fitting to dataset

So, I have a ODE system, it is a complex biochemical kinetic mechanism with six species changing over time. ...
3
votes
0answers
53 views

Fitting data to plot using errors as weights

I have some enzyme kinetics data that I want to fit to the Michaelis-Menten curve in order to obtain the kinetic parameters of the enzyme. Is it meaningful, statistically and functionally speaking, ...
0
votes
0answers
38 views

Solve an integral equation: to fit the given data with an integral of two functions?

I am trying to find an efficient way to solve the following equation $$h\left(b\right)=\int_{0}^{b}f\left(\frac{b-c}{1-c}\right)\frac{g\left(c\right)}{1-c}dc$$ where for $h(b)$ I have the data ...
2
votes
0answers
52 views

How can I fit the parameters describing a given 3D object such that its projected shape best matches the silhouette observed from a given location? [duplicate]

[I'm reposing my previous question to make it clearer]. I have data which are the longitudes (l) and latitudes (b) for the vertices of the edges of a shape as it appears to an observer at a given ...
1
vote
0answers
57 views

Optimizing orthogonal nonlinear regression code

I'm doing a simulation problem on the Langmuir adsorption model, where I need to obtain the model parameters from simulated data using the orthogonal nonlinear least-squares regression method. Here is ...
5
votes
1answer
75 views

Intersection of a ListPlot3D surface with a plane

I'm trying to use Mathematica to analyze some physics data from an experiment, more precisely, I have to fit a 2D data series with a one dimension function. At the moment I'm able to load and plot ...
1
vote
1answer
46 views

non linear Least Squares with model function given by ODE's

I have to fit to experimental data a model function given by a linear combination of functions y1(t) and y2(t) a1*y1(t) + a2*y2(t) with a1 and a2 ...
0
votes
0answers
35 views

FindFit returning Power::infy: Infinite expression

So, I'm having an issue trying to fit some data to a function with a 2nd order pole. I know there are other functions that fit the data, just fine ... but the model is from the literature, however the ...
0
votes
0answers
47 views

Investigating the correlation between this 2 set of data

The picture below shows the growth of the traffic and the total number of published articles on that website. Which functions can I use to investigate if there is a correlation between them? Both ...
1
vote
1answer
45 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: ...
1
vote
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 ...
4
votes
1answer
127 views

TimeSeriesModelFit incorrect?

I am trying to determine the optimal model for time series data (1592 observations). When I run TimeSeriesModelFit, Mathematica selects $AR(1)$ model, the estimated ...
1
vote
2answers
183 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 ...
3
votes
0answers
61 views

Custom Methods for NMinimize/NonLinearModelFit

Is there a way to write custom methods for NonLinearModelFit or NMinimize? To give background, I currently have a batch of code that uses NonLinearModelFit with NMinimize as the method to do ...
1
vote
2answers
82 views

NonlinearModelFit and plot with multiple parameters function

i ve got quite simple function: $f(t) = x1 * a(t) + x2 * b(t)$ and table of results like this one: t | f(t) | a(t) | b(t) ---------------------- 1 | 2 | 5 | 3 ---------------------- 2 | 4 ...
1
vote
0answers
51 views

Fitting a vector-valued model using Mathematica

I'm wondering if there is a way within Mathematica to perform some kind of parameter fitting on a vector-valued model function (in this case a model of electric field vectors). Essentially what I want ...
0
votes
1answer
61 views

How to do linear fit for 2D data points [closed]

I am very much new to Mathematica, and facing several difficulties. I used the following code Fit[{2, 4, 6, 8}, {1, x}, x] The output is ...
2
votes
1answer
66 views

Computing a Gamma function-Gaussian integral

I would like to compute the following function: Integrate[Gamma[k,0,Exp[-2 e x^2]],x] k is an integer and ...
-2
votes
2answers
47 views

How can I use NonlinearModelFit with multiple variables? [closed]

I am trying to find the coefficients for following equation: $\quad \quad f(x,\,y,\,z) = a (x^2)\, exp(b x + y^2) + c z^2 y$ using NonlinearModelFit. But I can't ...
1
vote
0answers
32 views

How does LinearModelFit handle cases where the design matrix rank is lower than the model terms?

So, I understand what this error means: ...
0
votes
1answer
53 views

Interpreting P-Value on ParameterTable

When using LinearModelFit[] we can generate a table of parameter values and statistics for the corresponding model using the property "ParameterTable". Looking in the documentation I can't find an ...
4
votes
1answer
105 views

Find fit of an experimental PDF

After quite some struggle, I managed to put up a code that is syntaxically correct. The goal is to find the parameters for a gamma distribution that best match experimental data. The data is a set of ...
15
votes
1answer
413 views

Difference between Fitting Algorithms

I am new to Mathematica, and I don´t quite understand, what the difference between the fitting algorithms Fit, FindFit, ...
4
votes
3answers
149 views

How to fit parameters in a system of coupled differential equations

Problem description: I'm studying a chemical reaction that can be modeled by a system of coupled differential equations, and I want to use measured data to determine the parameters that appear in the ...
6
votes
4answers
258 views

How to fit a surface to 3D data in Mathematica?

I have a set of data coordinates which is mostly compatible with an Ellipsoid: {{x1,y1,z1},{x2,y2,z2}, ... , {xn,yn,zn}} Now I want to find the best 3d volume ...
2
votes
1answer
82 views

How can I get the coefficient of the exponent from a nonlinear model fit?

I have been trying for over an hour now to get the numeric value for "HalfLifeN" from the code in the screenshot below. Not to mention mathematica simplifies ...
0
votes
1answer
37 views

Using Check[] on multiple statements

I am using a loop to run run multiple fits. If a fit fails, I don't want it to either appear in my data or to affect later fits so I am using the Check[] function to catch if any errors occurred (I'm ...
2
votes
1answer
38 views

Is this behavior of DistributionFitTest together with StableDistribution a bug?

I have been using DistributionFitTest to fit the following data: ...
2
votes
1answer
95 views

NonlinearModelFit: fit a vector-valued function to a data vector

I have a vector of data points: data = 10 Sin[#/10] + RandomVariate@NormalDistribution[] & /@ Range[200]; And I have model that provides the complete ...
0
votes
1answer
99 views

How to adjust excel data for NonlinearModelFit?

I'm really new to Mathematica and I'm facing a problem and would really appreciate some help! Maybe my question is similar to one described in How to fit 3 data sets to a model of 4 differential ...
1
vote
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 ...
0
votes
0answers
29 views

How to use FindFit to find the parameter in Laplace space(numerically inverting Laplace transforms)

I am trying to find the parameter in Laplace space, and a very simple example is shown below: I have known the solution $y_{laplace}$ in the laplace space is $a/s^2$, and I also have some discrete ...
8
votes
1answer
272 views

How can I improve my prediction for the end time of the Reddit button game?

There is an April Fools game on Reddit where users with accounts can press a button (once) to reset a 60 second countdown timer: https://www.reddit.com/r/thebutton ...
0
votes
2answers
123 views

Log Linear Fitting of a data: e.g. {xi,Log [yi]} and plotting the fit

I have a Log-Linear plot, and i'm unsure about how to fit a line to it. The data represents a I (current) vs V (voltage) curve. The exponential portion of this curve (linear in a Log-Linear plot) is: ...
5
votes
1answer
138 views

FindFit returns “tensors have incompatible shapes”

I'm trying to fit experimental data with FindFit and implicitly calculated function. It seems, that function works fine and satisfactorily approximates data when parameters are fed manually. However ...
0
votes
1answer
54 views

How to determine a function that fits a geological model

I have a problem. I am currently working on a code that works by comparing data (real or synthetic) to an earth model (described by earth layers, or in this particular, velocity (...
0
votes
0answers
36 views

Why does ParallelMap throw errors where Map does not?

I am encountering a problem with ParallelMap. I have a call in a large code base, part of which attempts to fit data in parallel using ...
4
votes
3answers
92 views

Better output for NonlinearModelFit “ParameterTable”

The Standard table fo parameters of NonlinearModelFit is obtained from NonlinearModelFit[{{0, 1}, {1, 2}, {3, 3}}, a + b*x, {a, b}, x] %["ParameterTable"]] I ...
1
vote
1answer
50 views

Precision of starting values in FindMinimum [closed]

I am currently working on an optimization of chemical kinetic model. Starting points for FindMinimum are defined as: ...
1
vote
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 ...
0
votes
0answers
44 views

Fitting an ellipse to data with a special constraint [duplicate]

I have a bunch of x,y scatter data and I am trying to fit an ellipse through them. I understand there are solutions for the fit where the data points are defined for a full or partial ellipse. ...
2
votes
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 ...
0
votes
1answer
89 views

Simultaneously fitting two data sets to two functions is too slow [closed]

I have to fit two data sets to two functions(eps1,eps2) with same parameters (w0,f,g) Initially, I know only one function ...
6
votes
1answer
99 views
0
votes
2answers
58 views

Curve fitting of a list and exclude some figure

I am a fresher of Mathematica and trying to program a list of digits. When I plot the diagram of the list, it shows that the figure at 12 is much larger than the others. Does anyone have idea on it? ...
0
votes
0answers
74 views

Decompose Point-Spread Function into Seidel Aberration/Zernike Polynomials

I have measured the point spread function (PSF of a microscope) and I want to quantify it. For that purpose I want to fit my PSF data to the primary Seidel optical aberrations (or Zernike Polynomials, ...
0
votes
0answers
44 views

combining separate data into pairs after reading from excel so I can run regression

I have the following code that reads data from an excel spreadsheet: ...
0
votes
0answers
48 views

Fit a complicated function to a constant with NonlinearModelFit

I wish to fit a complicated parametric function (logder, with lambda parameters) to a constant (L) in order to minimize its dependence with the variable k in a given interval. To do that, I use a ...
1
vote
1answer
44 views

Fitting data with a complex function, but requiring real parameters

I am trying to fit a complex data with a complex function, with the real fitting parameters. I was trying to put there constraints like this, but I got error: ...