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

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5
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1answer
266 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 ...
1
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0answers
66 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 ...
1
vote
1answer
245 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
vote
1answer
118 views

Fitting with roots of transcendental 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 transcendental equation dependent on a ...
0
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1answer
130 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
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0answers
291 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, t. ...
1
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1answer
233 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
128 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
136 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
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0answers
114 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
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1answer
220 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
110 views

Ordinary Least Squares (OLS) with RLink

I need to calculate the parameters b0, b1 and b2 in: ...
0
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1answer
99 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
85 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
66 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
189 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
401 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 ...
2
votes
2answers
190 views

FindFit working with Integrate but not NIntegrate - I am using “?NumericQ”

I'm having some syntax problems with finding a fit to an equation that doesn't have an analytical expression for it's integral. Because I think the problem is one of syntax, I am substituting a ...
2
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0answers
70 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 ...
3
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0answers
156 views

The CorrelationMatrix is equal to corrcoef of Matlab?

How can I generate a matrix which is equivalent to the results of the "correlation coefficients" command (corrcoef) in Matlab? When I make a LinearModelFit, I can get a CorrelationMatrix, but is this ...
11
votes
0answers
310 views

Implementation of Partial Least Squares (PLS)?

I'm looking for a PLS implementation for Wolfram Mathematica. I just can't seem to find any implementation for it - do you know one? In general, I'm a bit confused that there exist only so few ...
1
vote
0answers
129 views

Fitting curves with NonLinearModelFit not working with charge and discharge like data

I'm trying to get a reasonable fit out of mathematica, but i'm not very practical with it. I'm not that good with mathematica at all actually(like cleaniness of the code...). btw, here's my problem: ...
2
votes
1answer
118 views

FindDistributionParameters and Hypothesis Testing

Please excuse me if I am making any logical error in posting this question since I am not a math major. However, let me post my question. I am trying to fit multivariate parametric distribution to ...
2
votes
1answer
151 views

How do I find out what a Mathematica function is doing (which numerical method it uses and how)?

Long story short, I am working on a project which entails fixing a bug I have found in Mathematica (8 and 10). In general, I would like to know what a specific Mathematica function is actually doing ...
1
vote
1answer
97 views

“Power series” in Cos[n*x] for X coordinate of planetary ellipse

Consider the functions below: ...
1
vote
2answers
227 views

How to obtain the best possible NonlinearFit

Here is some sample data ...
4
votes
1answer
200 views

Find GeometricTransform from 3D object external surfaces to a positional point cloud data

I am looking for another way to approach this problem. Any suggestion on how to optimize the computing speed is welcome. I have a BSplineFunction which accurately ...
1
vote
1answer
164 views

Mixture coefficients and Parameter estimation for moving Normal distributions

I am searching for a way to do the following steps below. I am stumped and I have stumped a few profs too. Any help would be appreciated. I would like to import data from, say, excel or a .txt file ...
0
votes
2answers
69 views

Handling msg for fitting

I have a trivial question: I do Monte Carlo with some curve fitting. Now always when a random run creates a complex fitting solution it should write 1 in a Matrix. How can I handle such msgs in a ...
4
votes
1answer
117 views

Mystifying failure of NonlinearModelFit

Fitting the following two time-series (two repeats of the same exponential growth process) ...
3
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1answer
158 views

Troubles with FindFit for ODE

I need to use FindFit for ODE with arbitary number of parameters. This code (from documentation) works: ...
0
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1answer
115 views

Fitting data with inclusion of constraints

How do I find a fit for the dataS (see below) with the constraint that the parameter np is an integer, and that the parameters la+lc = 100. A weak attempt at this is provided below for a specific ...
16
votes
2answers
645 views

Curve fitting by running through hundreds of models and return the one with best fit

In the past, I used to solve a lot of my regression analysis (curve fitting) problems with a program called DataFit which runs on Windows. It has hundreds of regression models which it runs through in ...
2
votes
1answer
439 views

Fitting data to a circle with FindFit

I'm currently trying to use the Mathematica's FindFit command to fit a curve of some data to the bottom half of a circle. The data is of the form ...
5
votes
1answer
235 views

Forcing NonLinearModelFit through a point

Like the title says, is there a way to make an NLM fit pass through a specific point.
1
vote
1answer
101 views

Using List/Histogram Data As A Weighted Function?

I have a list of data points that I would like to use as a weighted function. The data represents the number of particles within a bin of a particle distribution. Ultimately I would like to multiply ...
2
votes
1answer
66 views

Is there a way to show some “weighted” residuals after LinearModelFit?

I am fitting some functions to some data and then I want to analyze the residuals of that fit. I'd like to see how those residuals compare to the values of the original data, hence my "weighted" in ...
0
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2answers
131 views
2
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3answers
162 views

BSpline or other curve through arbitrary ordered sequence of two-dimensional points

How does one create a BSplineCurve or other smooth curve passing through each point in an ordered list, where the curve may be non-simple, i.e., can double-back ...
3
votes
2answers
456 views

Best fit equation from a scanned image

I am trying to extract a curve from a scanned graph and find a best fit equation. For example, starting from: How could one find an equation starting from the image file ?
1
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0answers
132 views

Error associated with parameters in Minimize (or NMinimize) in discrete fitting

my problem goes as follows: I need to a discrete fit of a discrete function. Say I have the following made up data points, which are generated by the parabola ...
0
votes
0answers
286 views

Multi-peak fitting

Suppose we have a data set that looks like this: I have to fit this data to 9 peaks knowing μ and σ beforehand & have to ...
1
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0answers
84 views

Updating procedural fitting algorithm to more efficient style?

For some time now, I have used this procedural programming approach to fit data in my research that is too cumbersome for the built in Mathematica functions. (Although this simple example works fine ...
0
votes
1answer
207 views

Equation of line from loglog plot

Given some data that looks linear on a ListLogLogPlot, how can I find the correct equation (and particularly, the correct slope of the line)? I have a sample code here ...
0
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0answers
117 views

How to perform a distribution fit test to censored data

With following code I will get an error: ...
4
votes
2answers
150 views

Remove redundant parameters from equation

I have random expressions like (b1 x + b2 x)/(b3 + b4/b5 x) + Sin[b6 x] where $x$ is a variable and {b1, ..., b6} are parameters to be fitted. This expression is ...
0
votes
1answer
158 views

Non linear model fit

I need to fit this, but for some reason I cannot... data = {{0.617,0.8}, {0.605,0.6}, {0.5997,0.4}, {0.5972,0.2}, {0.5985,0.1}}; soln = NonlinearModelFit[data, {y - 2478.82*wlog[kc + 1]}, {y,w,k}, ...
10
votes
0answers
252 views

PenaltyFunction Option in NMinimize

I am curious if anybody has some experience in using the built-in Option "PenaltyFunction" in any of the numerical optimization functions like NMinimize. According to the documentation the user ...
7
votes
1answer
172 views

How to derive SinglePredictionBands from a NonlinearModelFit model

I have found NonlinearModelFit to be extremely useful in my work. Here I have fit 4 points to a function and am being asked to explain how the 95% SinglePredictionBands associated with the plot below ...
1
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0answers
80 views

Simultaneous fitting to multiple data sets with multiple variables and some common parameters [duplicate]

I am trying to fit two data sets to a function model described below which share a few common parameters. Say I have two functions with some common parameter(s) ...