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

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6
votes
1answer
81 views

Extracting fit weights directly from a FittedModel object

Suppose I have the following data: ...
6
votes
3answers
134 views

Fitting data with interdependence

I have an issue, of which I'm not sure it can be solved, with or without Mathematica. I feel as if it should be possible, but I'm quite clueless as to how. Some introduction is required. I'm working ...
3
votes
2answers
141 views

Automatically detect higher slope in numerical data (within a certain range)

Suppose the dataset data is part of some simulations whose results should follow a certain model. Here is data and its ...
1
vote
1answer
48 views

Linear Fit of multidimensional data

I am trying to find linear decomposition of vector B (of arbitrary dimension $n$) in the form : $B = \alpha_{1} C_{1} + \alpha_{2} C_{2} + ...$ where $C_{i}$ are known vectors (of dimension $n$) ...
2
votes
2answers
127 views

Finding the FWHM of a NonlinearModelFit gaussian [duplicate]

I have a NonlinearModelFit in a very large program, f1 = NonlinearModelFit[d1, a Exp[-(b (x - c1))^2] + yoff, {a, b}, x] Which is used in my program to produce ...
17
votes
2answers
255 views
+100

Sensitivity of NonlinearModelFit to model

I have come across a circumstance where NonlinearModelFit is very sensitive to the model used. I am aware that NonlinearModelFit ...
6
votes
3answers
144 views

Make NonlinearModelFit return continuous function

Suppose I want to fit the dataset ...
0
votes
0answers
74 views

Fitting Data using GeometricBrownianMotionProcess

I am trying to fit Data (see below) using a GeometricBrownianMotionProcess, and have attached two figures. One figure is that of the Data, and the other of the GeometricBrownianMotion for given ...
4
votes
0answers
94 views

Goodness of Fit of Copula Distribution

I am trying to find out goodness of fit of copula distribution, but Mathematica 10 gives me the same answer for each copula type. e.g ...
3
votes
2answers
131 views

Estimate parameters of AR1 process

I am trying to estimate the parameters of a series $Z_t=W_t^\beta$, where W_t follows an AR1 process with mean 2, $\rho=0.9$ and $\sigma=0.1$: $W_t = \rho W_{t-1} + (1-\rho) \bar{W} + \epsilon_t$ ...
1
vote
1answer
102 views

Why does FindFit work and NonlinearModelFit does not?

I have a somewhat complicated function that I have defined. ...
3
votes
2answers
66 views

How to use Evaluation Monitor in conjunction with NonlineaModelFit?

I am trying to find out how many function, gradient and hessian evaluations are made when i run NonlinearModelFit for example in this case ...
0
votes
1answer
99 views

How to speed up NonlinearModelFit applied on a NDSolve solution?

I'm trying to perform fittings of a model defined through a system of ODEs to data consisting of time courses of a measured quantity. As described in a previous question, the system of ODEs is as ...
2
votes
1answer
153 views

Fitting one set of data with two function

I have a set of data (42 points): ...
2
votes
1answer
79 views

Fails to apply NonlinearModelFit on a numerically evaluated model defined as a system of ODEs

I call for your help with because I'm getting troubles to fit a model defined through a system of ODEs. The system of ODEs is as follows: ...
5
votes
1answer
125 views

How are p-values in fittings estimated?

I am trying to understand how p-values retrieved in a ParameterTable estimated but I couldn't find any specific information in the documentation about this. For instance, considering ...
1
vote
0answers
72 views

NonlinearModelFit::nrnum error [closed]

I'm trying to fit data (including some small negative numbers at both extremes) to a normal distribution. ...
-1
votes
1answer
62 views

Pulling variable out of NonlinearModelFit [closed]

I have a fit, Dynamic[f1 = NonlinearModelFit[d1, a Exp[-(b (x - c1))^2] + yoff, {a, b}, x]] Where I need to be able to access ...
3
votes
2answers
102 views

Gauss Fit to List of 2D Points

I've been trying to find a solution to what I think is a common problem. I have a list of Data like ...
5
votes
1answer
101 views

FindFormula can't deal with the population data from Wolfram server

Bug introduced in 10.2 and persisting through 10.2 or later In the documentation of FindFormula, the first application of it is to predict the population of ...
0
votes
0answers
57 views

Modify measured values to improve NonlinearModelFit results

Problem: Measured data points have a random distribution of DC offsets (either +/- 0.65 mV), that came from an incorrect setting on the 24-bit ADC we were using. Essentially for each measured voltage ...
1
vote
1answer
101 views

Problem fitting when some data is missing

I have a problem fitting a function to data, where I only have the falling and rising edges of the data, with the peak having been capped and was wondering if you have some tips. The data should have ...
27
votes
2answers
493 views

What is behind Mathematica's experimental `FindFormula` function?

In version 10.2 there is a new experimental function: FindFormula. I suspect that a genetic programming algorithm (symbolic regression) is behind this new feature ...
0
votes
0answers
65 views

How to calculate the standard error of a parameter for a simple nonlinear fit?

I am trying to get the standard error of the estimate of a parameter in a simple nonlinear fit. I manage to get it for a linear fit. I used the formulation from a previous post. Here is my code for ...
3
votes
0answers
86 views

How to find the best fit for given input data? [closed]

I have the following data: ...
2
votes
1answer
79 views

Still more problems with Fitting, please help

I'm in a little over my head here and I'm fully aware of it, so I'm hoping for some help. I've been assigned to a project where I am given data: http://www.pastebin.ca/3061136 (Example Data) I ...
2
votes
3answers
185 views

Fitting and plotting Weibull distribution

How can I find the best fitted 2-parameter Weibull's distribution (PDF) to describe my data? How can i plot my data and estimated distribution all in one graph? How can I show/compare results of ...
2
votes
2answers
59 views

Using FindFit for a non-trivial complex function [duplicate]

I have data set which I would like to fit to the function $\quad \quad f(r) = A\cos(kr - \pi/4 + \phi_1)\times\exp(i(-2\log(r) + \phi_2))$, where $k$ is a constant I know and $(A,\phi_1,\phi_2)$ are ...
2
votes
2answers
64 views

Fit model with two dependent variables

Say I have an experiment that produces two values, for a given input. For example you get a complex response value. Now I have a model that - of course - also produces two dependent values for one ...
1
vote
1answer
73 views

Curve fitting data I imported from excel [closed]

This is my first time posting here, so sorry if I break any rules. There is this excel document from which I imported two columns of data to mathematica. I need to fit the data into a curve so that ...
0
votes
1answer
44 views

Mapping Linear Model Fit Over An Arbitrary Number of sets

I have multiple sets of data, and I want to apply Linear Model Fit sequentially to each set of data. For example, below tstlst contains 3 data sets. Right now I ...
3
votes
3answers
289 views

Fitting - Exponential

I'm trying to fit the following data using Mathematica, but unfortunately im not getting any decent results. ...
1
vote
2answers
88 views

TargetFunctions option in FindDistribution yields error

I have some data set that I am trying to find the maximums . I figured I could do this by fitting the many peaks of the dataset to Gaussian distributions and then finding the peaks of this data from ...
1
vote
0answers
98 views

Solution to heat equation with Neumann boundary conditions and lateral heat loss

I am conducting an experiment on heat conduction in a copper rod. To do so I am using a thin copper rod with several temperature probes, then I am going to compare the data with a solution to the heat ...
5
votes
1answer
202 views

Find a Fourier series from discrete data

I am trying to fit a Fourier cosine series to discrete data. I read through this, but I was not able to understand it. The data should be periodic with a period of $0.2 \text{ m}$, and it is the ...
0
votes
0answers
42 views

R^2 values for piecewise regression

So I've used NonlinearModelFit on a Piecewise function and gotten a nice little piecewise regression. This is what my code looks like: ...
-1
votes
1answer
85 views

NonlinearModelFit errors and precision

For this problem, I use a data set, which I've made available here. ...
1
vote
2answers
83 views

Non Linear Model Fit (Division by Zero Error Message)

Can someone please tell me why this expression returns error messages about division by zero. ...
1
vote
2answers
70 views

What is the role of the pattern object in this implementation?

In the documentation I found a nice idiom which allows me to do model fitting with interpolating functions. I think this kind of thing is amazing and a credit to the utility of an environment like ...
0
votes
0answers
28 views

Fitting problem: InterpolatingFunction can not be localised

I got simple data looking as follows {{541.447, 311752.}, {540.359, 311723.},.. I tried to fit it in mathematica for the first time with a function that usually ...
0
votes
0answers
36 views

Which one will gives best fitting result?

I want to find out the parameters A, B, and C of the ...
2
votes
1answer
87 views
2
votes
1answer
90 views

P-Values are inconsistent when using DistributionFitTest repeatedly

I am attempting to become more familiar with the DistributionFitTest, specifically the distributions it yields and their fittedness. What I have found is that when I generate random data, fit it, and ...
4
votes
1answer
96 views

Substituting ParametricNDSolve for NDSolve

This is my first post so let me know if I need to format things differently. I have been using NDSolve for most problems which optimize parameters for ODEs. I believe that ParametricNDSolve would be ...
0
votes
0answers
63 views

Finding values of a variable fitting a function and minimizing a list of expressions

I am trying to implement bootstrapping (https://en.wikipedia.org/wiki/Bootstrapping_(finance)) of CDS curve. To implement it I am trying to minimize a series of expressions so that each expression is ...
1
vote
1answer
85 views

Plotting data after fitting it to exponential function [closed]

I am trying to plot h vs t such that h fits a equation ...
3
votes
0answers
127 views

Fitting data to a complicated function

So, where to begin. I have a certain dataset that I want to fit to a function. However, the function is rather complicated (matrix inversions, linearsolve) and does in general not have a closed form ...
2
votes
1answer
100 views

Precision of LinearModelFit with Polynomials

I have a Problem regarding the fit of given points with a polynomial up to the fifth degree. tableofvalues=Import["tableofvalues.csv"] My polynomial is: ...
1
vote
1answer
58 views

Trouble fitting with NonlinearModelFit

I'am having a bit of a headache comparing the results from the NonlinearModelFit to a particular dataset. I have the following dataset, ...
2
votes
1answer
104 views

Find the best fitting function for some experimental data

I am almost new in Mathematica, and so I have some problems that may appear basic for you. I am given a set of data taken from an experiment. I am supposed to find the curve that best fits them. The ...