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Questions tagged [fitting]

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

2
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2answers
120 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: ...
2
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1answer
85 views

What is FindFormula returning?

I was playing around with FindFormula and am experiencing some odd behavior. I am running MMA 12.0.0.0 on a Windows 10, x86 architecture - if that matters. ...
0
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0answers
19 views

Covariance matrix from FindMinimum

Despite checking for quite some time online and in the docu, I cannot find an "easy" way to get the covariance matrix from FindMinimum. When FindMinimum has reached the local minimum, it returns the ...
0
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0answers
39 views

Well calculated Root Mean Square?

I am trying to estimate root-mean-square of data and fitted curve. However, i don't know it is working well or not. Can you guys give me any idea? ...
0
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0answers
59 views

find gravity acceleration (g) using FindFit

I need some help again, with this simple exercise: Use the data to determine g, but this time use the functional form T = 2 pi Sqrt[L/g] for the period T of a ...
1
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2answers
79 views

Fitting experimental data with a parametric function

How does one use a fitting routine such as NonlinearModelFit with a ParametricFunction? Example below: First let's generate some data: ...
1
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1answer
54 views

Help with NonlinearModelFit Error

I would like to ask if anybody can help me to find a way around solving this problem in Mathematica. I've tried solutions I found here but they don't seem to work. I need all the help I can get. ...
4
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2answers
99 views

Non Linear Model Fit - Fitting ODE to Data

Thank you everyone for your meaningful contributions! My Goal and Problem I'm trying to fit a particular ODE in a set of ODE's to experimental data. I've attempted to implement this by following the ...
1
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2answers
47 views

Estimating the uncertainty in the slope of a straight line given the uncertainty in the data points

Basically I have some datapoints on the form $(x_i,y_i)$ ...
0
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1answer
79 views

How to find a formula that models this plot? [duplicate]

Here is the data that I used to get this plot: ...
0
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0answers
53 views

Can Mathematica be used to fit these functions related to the Riemann Xi function $\xi(s)$ to a known probability distribution type?

This question is related to my Math Stack Exchange question at the following link: Question on Probability Distributions Related to the Riemann Xi Function $\xi(s)$ The definitions below are for $x&...
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0answers
59 views
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0answers
40 views

What is optimized for each available FitRegularization setting?

Fit and FindFit now have a FitRegularization option, but the documentation is brief. What is optimized/minimized when each available setting is used?
1
vote
1answer
62 views

Weibull statistics

I have two data sets am interested in finding the weibull modulus and characteristics strength for the two data sets and plotting the data seperately but on the same graph Material (a) 723, 684, ...
6
votes
1answer
223 views

How could this asymptotic expansion be obtained?

I must precise that I am a very limited user of Mathematica (I can only run it from time when going at university). Working this problem, I found that $$\sigma_n=(1)^n\frac{\pi}{2} \big( j_{0,n+1} \,...
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0answers
43 views

Force FindFormula to avoid Piecewise in the result?

Is it possible to provide any arguments to FindFormula to force it to avoid using Piecewise in the result, but instead try to ...
-1
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1answer
41 views

Selecting method and using Abs[] for FindFit

I'm trying to fit the following list data ...
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0answers
36 views

Getting a PDF from a NonlinearFitModel

With the help of @JimB, I could fit some experimental data with a CDF using NonLinearFitModel. The set of data is the following: ...
0
votes
2answers
63 views

How to generate two non-overlapping LogNormalDistribution and their CDF?

I'd like to know how to generate two LogNormalDistribution with the same standart deviation and, if possible, get the associated CDF. To contextualize, I'm trying ...
0
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0answers
35 views

How to fit experimental data with by numerical integration?

folks. I'm a begginer with Mathematica and all I know is just a few basics commands and i'm trying to improve it. I have this list of experimental data taken from a paper which describes the ...
0
votes
1answer
50 views

How to fit one function into the form of another?

I have a slightly complicated periodic function of one variable t, say g[t]. I want to do a least squares fit of that function ...
0
votes
1answer
33 views

Table and NonlinearModelFit

I am trying to make data and fit it tp a power law model. but it doesn't work. I don't know what the problem is. ...
0
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0answers
63 views

How can I fit a function to another function?

I want to fit the gaussian function to power law function from the end of gaussian fitting curve to the peak of it, ...
0
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1answer
68 views

Model for log-inear data

I am trying to fit the following data with y axis on a log scale. I used the following model to fit the data but without success. Can anyone help me suggest a proper model? ...
2
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2answers
72 views

LinearModelFit with Standardized data

I have a small data set of six points: ...
1
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1answer
65 views

Curve Fitting using known Points [closed]

In this answer, David Stork said that my question could be solved using "simple curve fitting with different numbers of even polynomial rank" in Mathematica. How would I do that (an equation that goes ...
1
vote
1answer
64 views

Problem with fit

I am trying to find a proper matching function for the following data set: ...
0
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0answers
40 views

Creating a prediction/distribution based on several years of data

So I have several years of data from a survey. For each year I've used FindDistribution and Predict to see if I can fit the data. Here's one example Where I used FindDistribution to get ...
1
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1answer
103 views

How to fit my data to an ode

Here is system of ODEs and data, where I am trying to use the real data to estimate some governing parameters. ...
0
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1answer
55 views

Errors in Gaussian fitting curve [closed]

I fitted simulation data with Gaussian fitting curve, ...
4
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0answers
94 views

Fit Markov Chain

Assume a simple Markov Chain with the transition matrix ...
0
votes
1answer
45 views

Method for constrained NonlinearModelFit with NDSolve

I'm trying to fit some data with a system of differential equations : ...
0
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1answer
48 views

NonlinearModelFit of an NDSolve result

I have some data : ...
0
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0answers
43 views

Estimated LogMultinormalDistribution

How to use procedures designed for EventData for an event data in the bivariate form? That means the bivariate data containing each of the four combinations ...
1
vote
1answer
56 views

Least squares fit of a symmetric linear system

I have $q$ measurements with $p$ different excitations. In one special case, they might be equal in length. For example, I might have 12 measurements ($q=12$) with three excitations each ($p = 3$), ...
1
vote
1answer
65 views

How do I separate all local maxima and local minima of my function?

This question (and the first answer in particular), teaches us how to find all the local maxima and minima of a function. My question is: how can I separate the maxima from the minima? My goal is to ...
1
vote
2answers
43 views

Using FittedModel without clashing symbols

For some FittedModel, the "BestFitParameters" are given in terms of the symbols used to define the model. ...
2
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1answer
85 views

How to reproduce old SplineFit function?

Prior to version 8, Mathematica included a SplineFit function that could be used, for example, in the form: ...
0
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1answer
68 views

How to do a fit on multiple peak with a voigt function

I looked a lot on the other questions to do that but I can't find a way to do it properly. So here is my question. I have a spectrum of OH and I would like to do a voigt fit on every peak it has to be ...
3
votes
2answers
185 views

Determining multivariate least squares with constraint

I have some composition data for a geological sample and its constituent minerals. I want to estimate the proportions of the minerals that make up the bulk sample. This is essentially a mass balance ...
1
vote
1answer
58 views

Attaching independent variable values to data for curve fitting

I have a data set of $10^4$ entries. I want to plot the last $2000$ data with the same argument at $x$ axis and fit a curve. That means the range of $x$ axis will be $8001$ to $10000$ incremented by $...
6
votes
2answers
137 views

How to speed up Voigt profile fits?

Voigt profile fits in Mathematica seem terribly slow. For an example data set with 81 points a corresponding fitting procedures for Voigt fits is >1000 times slower than for Gaussian or Lorentzian ...
3
votes
2answers
72 views

Generating FittedModels from vector-valued linear model fits

I have vector-valued data with normally distributed noise that I want to analyse. Assumptions on data can be made; in this specific example, it's expected that components of fitted vector values ...
3
votes
1answer
51 views

Using an offset variable in a Poisson GeneralizedLinearModelFit

In section "2.6 Exposure: Modeling Over Time, Area, and Space" of his book "Modeling Count Data" Joseph M Hilbe uses an offset (exposure) variable in his Poisson regression analysis of the FASTRAK ...
2
votes
1answer
59 views

Fitting data with 3 linear fits

I have a dataset that can be easily approximated by a piecewise function composing of 3 linear functions, but i am unable to get an accurate fit once the third linear function is required. The model ...
0
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0answers
51 views

Peak convolution

I am not an expert of wolfram mathematica, anyhow I decided to use it to perform analysis on some data I acquired. I found on this website a question about how to do peak deconvolution and I tried to ...
3
votes
1answer
74 views

What is a proper way to represent multidimensional data in TemporalData?

A TemporalData object can host multiple paths or it can admit a ValueDimensions option value greater than unity. In the former ...
0
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0answers
42 views

fitting different data sets with one same model with NonlinearModelFit [duplicate]

I have a bunch of list data sets, like 6 or 8 of them. They are 2D and look similar. Both x axis and y axis have variance (in each measurement, x axis also changed a little bit).I know the fitting ...
5
votes
1answer
340 views

Should a new user just default to LinearModelFit (vs Fit) [duplicate]

I tried searching but the noise in the responses is high due to 'fit' being both a function and a valid term. If I'm new to Mathematica should I just default to ...
3
votes
2answers
102 views

Optimize/fit data for 2 variables described by three functions

I have three equations that describe how parameters change: $$N_{1}(T,f)=f \ e^{-T (\sigma^{1}_c +\sigma^{1}_f)}$$ $$N_{2}(T,f)=-\frac{f \sigma^{1}_c \ (e^{-T (\sigma^{1}_c +\sigma^{1}_f)}-e^{-T \...