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

learn more… | top users | synonyms (3)

0
votes
1answer
50 views

Importing Data to interpolation

I have an external file in extension XLS with looks as follows: This file can be obtained by the link below: Velocidade Angular With certainty this file is generating a list inappropriate for the ...
3
votes
3answers
128 views

Simultaneous plotting

For my experiment, I have to simultaneously fit the real part and imaginary part of cavity reflection data which is given here column 1: frequency, column 2: reflection magnitude, column 3: phase I ...
0
votes
1answer
30 views

Interpolating data while imposing the behavior of a cumulative distribution function

I would like to interpolate a data set which represents a curve of an empirical cumulative distribution function (CDF). Hence, the y entries are between 0 and 1, continuous and non-decreasing, and at ...
0
votes
0answers
38 views

FindFit with compiled function [on hold]

I try to fit parameters of my experimental data by FindFit. For the model function I use a compiled function, that does numerical calculations. Unfortunately, I get ...
1
vote
0answers
67 views

polar form of generalized superellipse (not Gielis formula!)

I am looking for the polar form of the following generalized superelliptic shape such that I can use it with NonLinearModelFit for curve fitting to data: $$ \left |...
1
vote
1answer
65 views

Predicting the initial conditions of orbits inside a closed curve

I have a data file containing the four orbital element $(x,y,p_x,p_y)$ of a two-dimensional closed loop orbit. Note that the exact implicit equation of the orbit is not known. The plot of the 2D ...
5
votes
0answers
78 views

Softmax Regression Classification Algorithm

I'm following the Stanford Machine Learning course while simultaneously developing my Mathematica abilities. I'm having issues with my Softmax Classifier implementation (for ref, have a look at these ...
1
vote
2answers
98 views

Complex Fit, using NMinimize?

I'm having trouble fitting this complex data: ...
0
votes
1answer
35 views

NonlinearModelFit error: the function value is not a list of real numbers with dimensions {101} at {a,k,m0} = \ {1.,1.,1.} [on hold]

So I'm trying to find a sigmoidal fit for my numerical solutions of these two ODEs but I keep getting an error and I don't know how to get around it. Here's my code: ...
14
votes
2answers
638 views

Fit a function to data so that fit is always equal or less than the data

I have a set of measurement data and I try to fit there a function (a Exp[b x] + c Exp[d x] - o). I have two problems: The fit function does not converge nor ...
0
votes
1answer
87 views

Data Fitting problem

I'm having this kind of data, and I know what possibly the equation is, i suspect this has a sine equation but the plot not really seems sinusoid. so what possibly the equation is so i can do the ...
2
votes
2answers
117 views

Nonlinear Fit sometimes does a good job and sometimes doesn't

So I'm trying to fit data, for all my data, the same fitting function can be used. Sometimes the fits actually FIT really well. Sometimes they just look completely random. Here's an example of it ...
0
votes
0answers
56 views

Solve equations involving summation expressions in Mathematica

I am trying to solve the simple linear regression equation analytically in Mathematica (not using builtin functions). I managed to calculate the gradient as follows f is loss function using RSS and ...
0
votes
0answers
36 views

Minimization With Complicated Divergent Model

I´m trying to use a minimization of a $\chi^2$ function (or similarly a fit) of some data with a complicated function. The problem is that the function has some divergences, and thus the problem ...
0
votes
1answer
52 views

Using LinearModelFit, how can I test the hypothesis $\beta=c$ with $c\neq 0$?

Assuming a simple linear model $y=x\beta+u$, is there a way to test the hypothesis $\beta=c$ with $c\neq 0$, using the LinearModelFit?
0
votes
1answer
65 views

FindFit works, NonlinearModelFit doesn't

I have a problem using NonlinearModelFit vs FindFit. Here is my code. ...
-2
votes
1answer
117 views
0
votes
2answers
59 views

Fitting log-linear data

I am using NonlinearModelFit to extract the gradient of what appears to be linear data in a logplot: ...
20
votes
3answers
3k views

Fitting fractional complex data with NonlinearModelfit

I've difficulites with the NonlinearModelFit function. In principle Mathematica should be able to deal with complex data. E.g. if I define the following table <...
0
votes
0answers
29 views

data fit using second order PDE

I'm trying to find the parameter for second order PDE using data. i don't know what is the error of that, ...
1
vote
2answers
82 views

How to calculate unknown parameters

I have measurement data from impact test-test specimen location (Charpy). I am used by the plotting in excel this formula hyperbolical tan Y=y0+a*tanh[(t-x0)/b] ...
2
votes
1answer
65 views

Linear regression

I have a sequence of data: data = {0.647888, 0.522495, 0.454224, 0.417054, 0.396816, 0.385798, 0.379799, 0.376532, 0.374754, 0.373786, 0.373259, 0.372972} How ...
1
vote
0answers
101 views

Fitting Three-Dimensional Data with Parameters

I have been trying to fit a model of rate equations to data of three dimensions. The rate equations in my model are as follows. ...
0
votes
0answers
57 views

Numerical fitting trajectory to model that has NDSolve

I have a model which describes the motion of an object on a plane. ...
1
vote
1answer
86 views

package for calculating exponent of power law distribution

There are some packages to fitting power law to empirical date in "R", "matlab", "python" Here with maximum likelihood method As it said here. Does it exist similar package in Mathematica?
7
votes
3answers
138 views

Locally Weighted Linear Regression

I am following the online Stanford Course in Machine Learning and I am trying to implement the algorithms on the fly in Mathematica. Currently, I have issues with minimizing the Locally Weighted ...
0
votes
0answers
31 views

Use “FindFit” for Multi-variable Polynomial Fit

I'm interested in defining three input vectors: $L=\{L_{1}, \ldots, L_{N} \}$ $W=\{W_{1}, \ldots, W_{N} \}$ $Q=\{Q_{1}, \ldots, Q_{N} \}$ and I'm hoping to be able to input a number for each of ...
1
vote
1answer
185 views

Fitting data to an Normal Inverse Gaussian distribution

I am using data which I suspect is distributed according to the Normal Inverse Gaussian distribution (NIG). The literature says that the 4 parameters of the NIG distribution can be estimated from the ...
8
votes
2answers
140 views

Using StepMonitor/EvaluationMonitor with DifferentialEvolution in NMinimize

My question about tracking the progress of a minimisation/fitting process is two-fold: 1. The first part of my question can be considered a slight duplicate/follow-up of this question. There the OP ...
-3
votes
1answer
43 views

importing mortality rates [closed]

In[1]=dataFrance = Import["G:\french female death rates.xlsx"] Out[1]={{{""}, {""}, {""}, {""}, {""}, {""}, {""}, {""}, {""}, {""}, {"0 \ 0.003531 "}, {"1 0.000312 "}, {"2 0....
1
vote
1answer
66 views

forecasting for mortality using a logistic regression

I need to know how to do a forecasting for mortality using a logistic regression, can somebody help? ...
3
votes
1answer
72 views

Filtering Background with resonance or Peaks

I have some data, the blue curve which I want to filter out the background to get a flat signal with dips(Idea is to divide signal (except the dips) by the background). The orange curve is my best ...
0
votes
1answer
56 views

How to force a Range on Fit?

I have 1001 points between {x,-5, 5}. I wanted to fit a polynomial over the data but when i try: Fit[Flatten[data], {0, x, x^2, x^4, x^5, x^6}, x] ... the range ...
6
votes
2answers
196 views

How to measure accuracy of prediction distribution?

I have been trying to come op with a way to test if my dataset follows a Poisson distribution. Normally one would use the DistributionFitTest function, but here is ...
3
votes
2answers
255 views

Mathematica Interpolation or approximation

I have lists of points X and Y. {1212,1216,1217,1219...}, {1,2,3,4,5,6...} I combine ...
3
votes
1answer
59 views

Looking for a convenient way to replace a large data sample with an analytic approximation

Suppose that data is a large data sample, and that Histogram[data] produces a very smooth-looking distribution. Since ...
2
votes
1answer
130 views
1
vote
1answer
69 views

NonlinearModelFit memory problem

I have a problem while trying to make a nonlinear fit of the following data: qn = NSolve[Tan[q] == 3*q/(3 + 1870715*q^2) && 0 < q <= 65, q] ...
3
votes
0answers
47 views

PearsonChiSquareTest for count/frequency data?

I read with interest a previous question on the PearsonChiSquareTest from a few years ago, and one answer was very helpful: Performing a chi-square goodness of fit ...
1
vote
2answers
60 views

Nonlinear fitting of a Gaussian beam model

I am having some troubles with the NonlinearModelFit function. However hard I try, I cannot get a nice fit curve for the data points. I know the parameter "a" is about 15*10^-6 but even if I plug in ...
0
votes
0answers
36 views

Is it possible to get the error estimates of predicted values computed by FindMinimum using the Levenberg Marquardt method?

I use the LevenbergMarquardt method of the FindMinimum function to minimize a residual function (mathematical-optimization). This residual function is computed from experimental data and the solution ...
2
votes
3answers
166 views

Use NMinimize instead of FindFit for constrained search (of coefficients)

(My problem is more complex, but let us formulate it through this example) I am trying to find the best polynomial approximation to the following function ...
2
votes
0answers
103 views
0
votes
1answer
42 views

Independent test of residuals, absolute member equal zero

Does Mathematica offer any test for confirm independence of residuals? except DurbinWatsonD. And I would like to ask how to make some test in regress function which tests absolute member equal zero. I ...