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

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3
votes
3answers
57 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
44 views

Precision of starting values in FindMinimum [on hold]

I am currently working on an optimization of chemical kinetic model. Starting points for FindMinimum are defined as: ...
1
vote
1answer
42 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 ...
-3
votes
0answers
54 views

How can I tell that I have a good least squares fit? [closed]

Given a data set $(x_n,\,y_n)$ and an algorithm expression, say linear fitting $y = a x + b$, I can always find $a$ and $b$ which minimize $\sum(y-y_n)^2$ in my parameter space. Even if $a$ and $b$ ...
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
44 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
72 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 ...
1
vote
0answers
52 views

Fitting data to a derivative model

I just started using Mathematica. I would like to use Mathematica to do non-linear regression. My model equation is : ...
6
votes
1answer
76 views
0
votes
2answers
55 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
42 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
39 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
26 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
36 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: ...
7
votes
1answer
235 views

Computing launch parameters for hitting a point in 3D with projectile under influence of wind

The end goal of this problem is to compute functions which describe the launch parameters which are needed to hit a specified goal in 3D in the presence of wind disturbances. This is as far I have ...
0
votes
2answers
50 views

Fitting data in form $f = f_0 + c A^x$

The Fit[] function in Mathematica can fit data in form of $f = f_0+c_1x+c_2x^2+...$ ($f_0$ and $c_i$ are unknown constants), is there a function can fit date in ...
3
votes
2answers
68 views

PredictionBands and the presence of {0,0} point

We know from this post, that the default fitting method cannot handle data with a {0,0} point, and that there are alternative methods. But, with these alternative methods, the prediction bands ...
1
vote
1answer
60 views

Fitting Legendre polynomial - Integer constraints in Fitting functions

I have some data in the form of {theta,y} and I am trying to fit a Legendre polynomial to it, however I don't know how I can get it to vary the m and l parameters in integer increments as I don't know ...
4
votes
1answer
79 views

FindFit runs extremely slow for my Function,how do I optimize this?

My function is the first order Bessel Function, and I am basically just trying to get this to fit in a way that does not take forever. I define the function as follows, (it seems to work faster if I ...
1
vote
1answer
37 views

LogitModelFit bias term when using design matrix

I'm using the LogitModelFit function with a 32-columns design matrix and 0 or 1 output vector: LogitModelFit[{datax, datay}]. ...
1
vote
2answers
61 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
vote
0answers
19 views

Fit a custom process to a data: inhomogeneous 2-state Markov chain

I would like to fit a custom process - a time inhomogeneous 2-state Markov chain, to data. The time inhomogeneity is a result of the transition probabilities varying sinusoidally through time with a ...
0
votes
1answer
36 views

NonlinearModelFit returning unexpected result

I am attempting to perform a weighted fit of some data. The Fit function produces the correct quadratic fit, which I am fine with, but it does not appear to support ...
2
votes
2answers
54 views

How to do dynamic range selection for data fitting in Log plot?

In linear plot, this can be achived by Locator like this: http://mathematica.stackexchange.com/a/24935/13580 ...
0
votes
0answers
39 views

How to control precision of parameters in NonlinearModelFit?

I am using NonlinearModelFit for fitting a dataset to some complex numerical model function that depends on a few parameters. The final required precision of these parameters is very low, like 3 ...
0
votes
1answer
38 views

ANOVA on data with different lengths

I have data in the following form: ...
2
votes
0answers
49 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. ...
3
votes
2answers
91 views

FindFit “is not a real number” error when fitting a parametric function to the data

I am using Mathematica's FindFit function to fit a parametric solution to my data and I am getting the error ...
2
votes
2answers
86 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 ...
0
votes
0answers
40 views

NonlinearModelFit not hunting for good values

I have the following data which come from complex values but I have turned them into a 3D list ...
8
votes
0answers
115 views

How can the Theil-Sen estimator be made to work on larger datasets?

The Theil-Sen estimator finds the slope and intercept of a line passing through a set of points by calculating the median slope and median intercept of the set of lines passing through all possible ...
1
vote
1answer
91 views

Is there any strategy to have a compiled version of FindFit or NonlinearModelFit?

Disclaimer: This is not a precise question with a definite answer. I know that neither FindFit nor NonlinearModelFit is in the ...
0
votes
0answers
35 views

How do I add custom deviation when using LinearModelFit?

I have a set of data in the form a list S1={{x,y},{x,y}} etc. I also have a function that calculates a corrected standard deviation in the y direction for ...
0
votes
1answer
80 views

Calculating a function whose input is stored in a Table [closed]

I am trying to evaluate this integral to get the output as a function of t. Now, I have a table which contains the values of δ ...
1
vote
1answer
122 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 ...
0
votes
0answers
76 views

Expand a fitting using FindFit[]

I need to implement multidimensional optimization using FindFit[]. But it's essential to exclude some parameters from the main procedure of optimization and to move on from direct optimization in ...
1
vote
1answer
51 views

Fitting with roots of trascendental equation

I'm new to this community and my first question probably reflect my lack of confidence with Mathematica. My problem is the following: I find the roots of a trascendental equation dependent on a ...
0
votes
1answer
65 views

LinearModelFit - Number of unique basis functions & Invalid variable errors

I'm having trouble with a simple linear fit model. Here is my code ...
0
votes
0answers
75 views

Extracting parameters from a fitted function

Let's say I have written a function which performs convolution and returns value calculated for the time чtч. ...
1
vote
1answer
78 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 ...
0
votes
2answers
99 views

How to fit points in a picture using locators

I've got a problem doing some analysis work on some of my spectra. I am basically looking for features that look like parabolas. In need of a tool to quickly find two parabolas in a spectrum (they are ...
3
votes
1answer
95 views

How to make a diagnostic plot for the regression?

Context I am interested in LinearModelFit, and would like to make diagnostic plots using Mathematica. I cannot find them in Mathematica document center. For example, the following R program makes ...
1
vote
0answers
107 views

How well does my function fit data? [duplicate]

Oleksandr Karsten suggested me to mark the difference between this question and the one that is already answered: in the other question it is calculated a ...
0
votes
1answer
83 views

NonlinearModelFit - “Encountered a gradient that is effectively zero”, all variables are 1, 1, 1 [duplicate]

I have data of the form {149.45, 0.371093}, {149.362, 0.375976}, {149.277, 0.380858}, ... }, where each element of the list is {x, y}. The plot of this, using ListPlot, gives an approximate Gaussian. ...
3
votes
1answer
62 views

Ordinary Least Squares (OLS) with RLink

I need to calculate the parameters b0, b1 and b2 in: ...
0
votes
0answers
18 views

Binomial Regression where n > 1

I am not well versed in Generalized Linear Models, but am trying to use this approach to model some discrete data. I have binomial data where the sample size for each observation is the same size, ...
0
votes
1answer
59 views

Regression with 3 variables

I'm trying to find a function starting from its values but I can't find anything related to functions with 2 variables and I don't know how to go on. So, given this sample data, I'd like to know how ...
0
votes
1answer
52 views

How to fit this data to be used in NIntegrate later?

I have a list of data points that resemble a chi-squared distribution (long tailed gaussian) that I am having trouble fitting or finding an equation with. The goal is to use the fitted equation in an ...
1
vote
1answer
82 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 ...
3
votes
1answer
125 views

Test Goodness of fit for FindFit

Is there any way to get an estimate of the goodness of fit from FindFit, for instance getting the final error? The documentation doesn't provide any hints, and a quick Google search didn't return any ...