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

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1
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0answers
34 views

Non-aggregated solution for NonlinearModelFit [closed]

I try to fit a rather simple functional form to data, lm = NonlinearModelFit[estdata, a + b*x^2, {a, b}, x] obtaining ...
0
votes
0answers
75 views

Convergence Problem using FindFit

I have the following input where there is a convergence problem in the FindFit as shown in the attached figure.The figure shows 2 plots: one of the real data and the other of the fitted line. Any ...
3
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1answer
85 views

Saving data from NonlinearModelFit

If you use NonlinearModelFit the results are put into some sort of output package. How do you save these packages so that you can go back to them later? My particular problem is that I generating ...
5
votes
3answers
449 views

Finding exponential model from data [duplicate]

I'm trying to find an exponential model from data for a homework problem. There is an accompanying video explaining how to do the bigger problem but it omits any instructions on the step where the ...
1
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1answer
217 views

General F statistic and p value in LinearModelFit

Many statistical packages provide a "F statistic" and the corresponding p value in their output of a multiple linear regression. I don't find that in the parameters of the Mathematica function ...
1
vote
1answer
117 views

Fitting composed model to experimental data

I have mathematical model based on equation: $y(x) = 1 - \sum_{b=1}^{\inf} 2c_b \sin(c_b x/L) \exp(ax) $ (1), where $c_b$ are the positive roots of equation: $c_b \cot c_b + aL = 0$ (2). $L$ is a ...
6
votes
1answer
291 views

Using Manipulate to dynamically correct the baseline of a signal

i have data with a baseline and will correct it with a polynomial fit using Manipulate to see immediatly the changes in the resulting spectrum. It works so far, but ...
9
votes
2answers
2k views

What is the best distribution for my histogram?

I defined a security bound for a random walk (cube with 15 lengh) and i have this code to obtain a sample of the random times at which the random walk crosses the boundary for the first time: ...
6
votes
0answers
239 views

Problems extending NelderMeadMinimize into 2D

Update The eventual route I followed was to adapt a version of the NM-simplex written in C and link to it with MathLink. Once I've tested this out fully I'll post it here. I've been playing around ...
3
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0answers
183 views

Stuck in local minimum in NonlinearModelFit using Simulated Annealing? [closed]

I recorded a set of experimental rates $r = r(c,T,P)$ at 2 values of $c$ and >15 values of $T$. $r(c,T,P)$ obeys the following functional form: $$ r(c,T,P) = ...
4
votes
1answer
301 views

Fitting numerical model to experimental data

I have diffusion equation with the initial/boundary conditions: ...
3
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1answer
161 views

FindFit with parameters which are simultaneously in initial conditions

I have RLC circuit. I would like to find R and L by using FindFit, but L is in initial condition and I have problem with it. Could you help me ? ...
2
votes
1answer
200 views

Non-linear curve fitting with multiple parameters and conditional expression

The above integral(Bloch Gruneissen formula) is what i like to fit with my experimental data.I am new to Mathematica. To cross-check the fit results obtained in other software, I try to fit with my ...
23
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5answers
2k views

Mathematica Implementations of the Random Forest algorithm

Is anyone aware of Mathematica use/implementation of Random Forest algorithm?
-1
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1answer
135 views

Formatting and inserting a parameter table into a plot

I'm fitting data, and I want to put the parameter table generated by NoninearModelFit into the plot. How can I do that in a reasonable way? I want to format the ...
4
votes
1answer
202 views

Removing Linear drift from an oscillating data

I have an array of 800,000 data measured at 1.1s time gap. It is oscillating data but has clear linear drift. I want to remove this linear drift. But the estimates by ...
3
votes
2answers
423 views

SinglePredictionBands versus MeanPredictionBands from NonlinearModelFit

From my Statistics lectures I know the term confidence and prediction interval, whereas the confidence interval is smaller than the prediction interval. If I plot the mean and single prediction bands ...
1
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0answers
107 views

Cross-validation of a FittedModel

Although I would know how to perform cross-validation tests after fitting a model using a function like NonLinearModelFit, I wonder if there is a way to do this providing the right parameters to the ...
40
votes
4answers
3k views

How to visualize 3D fit

I have a data set of x,y,z values and I fit a function of x,y to the data. This works, but I can't come up with a nice way to ...
3
votes
0answers
159 views

Memory problem in Mathematica 10

I'm having a problem with memory. I'm doing nonliner fits of several data lists to a system of differential equations. When I evaluate the "Do" cycle the memory grows with the iteration step up to my ...
27
votes
4answers
750 views

What is the natural way of using Dataset to get a FittedModel?

The new Dataset in Mathematica 10 is a great addition to the language, potentially reducing the convenience gap with R. Given this, I would like to understand what the equivalent simple or natural ...
1
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0answers
48 views

How to fit data with numerical solution of system of parametric ODE? [duplicate]

I need to find the parameters (k1,k2,k3,k4,k1r,k2r,k3r,k4r) that fit my data (list of [Intensity, time]) using the function ...
0
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1answer
66 views
1
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0answers
221 views

Developing easy code to apply Delta Method to generate prediction bands for custom distributions

I think that this is an interesting issue for all those who when to not only adjust one prediction function, but also to obtain the prediction bands to asses the graphical or tabular error I'm trying ...
3
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3answers
200 views

Zero-order interpolation not going fully around

Connected to this question, I want to do a zero-order interpolation of a bunch of datapoints which is periodic. The code I use is as follows: ...
0
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1answer
94 views

Constraining some rows from LeastSquares to lines

For two matrices, A and B, with dimensions {n,p} and ...
0
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0answers
67 views

No real number fitting double exponential in Mathematica

I am trying to fit a double exponential curve to my data, but I got the error saying there are non real number. Also I tried with starting values for my 4 parameters, but this does not work either. ...
3
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3answers
253 views
2
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0answers
73 views

Why do EstimatedDistribution and DistributionFitTest work this way

I am fitting some time-series data to both a stable distribution and a normal distribution in order to assess the goodness of fit of each. Along the way I encountered the following confusing result. ...
3
votes
3answers
190 views

Fitting the Plot by fourier Series of either sine or cosine

I have list of data and its plot and I don't know how to fit the plot with fourier series of either sine or cosine. Full Data: ...
0
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1answer
68 views

What is the definition of FitResiduals

What is the definition of FitResiduals in Mathematica? I could not find its definition in the Mathematica help. Is it the same as chi squared?
0
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1answer
276 views

Logarithmic curve fit in data

I have the following data which are the theoretical: ...
9
votes
2answers
460 views

Does FindFit support complex numbers or doesn't it?

Inspired by this previous question: Findfit doesn't give the good fit; Changing the starting values will not change the results. Consider the following complex-valued dataset. ...
1
vote
3answers
1k views

Why does FindFit seem to have trouble fitting exponential data?

I have 4 data points. t is in minutes, and y is radioactive counts per minute. When I input the following lines: ...
2
votes
1answer
139 views

Piecewise conditions with a parametric PDE

I'm using ParametricNDsolve to check best fit of a model (function Eb1) with some data, and I have four free parameters I want to test. I can easily construct a Parametric solution between the two ...
0
votes
1answer
434 views

Fitting data to a Poisson distribution

I'm trying to fit a Poisson Distribution to data produced in a lab. I've successfully made a Histogram of the data, which looks like: However, when I try to fit the Poisson Distribution using: ...
1
vote
2answers
86 views

FindFit is producing a list of imaginary numbers when there is non

I am trying to find the fit of an equation to some data and mathematica thinks there is a list of imaginary values. My data is all real positive number. ...
0
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0answers
94 views

Horizontal shift in fitting data by a sinusoidal nonlinear model [duplicate]

I have data that can apparently be fitted by a sinusoidal function in form $D+A\sin(B(x-\frac CB))$. I tried doing the best fit in Mathematica using ...
0
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2answers
382 views

Error function fit of data

I have this experimental data set which I know should follow the Complementary error function. My goal is to find the σ of the associated gaussian distribution. However, I cannot seem to do it in ...
2
votes
3answers
223 views

To obtain an equation for a given curve

I have obtained the graph, I would like to know its equation. The graph seems to be a hyperbolic spiral which, its equation reads, $r = a/\theta$. I read here and also, but these are concerning the ...
0
votes
0answers
54 views

How do I constrain the result of fitting my non-linear model to be greater then 0

fitresulty21 = NonlinearModelFit[ydata21, {funfit[y, σ, A, B, x1, d, d/2], A > 0}, {{x1, 20}, {σ, 3}, {A, 200}, {B, 2000}, {d, 110}}, y]; ...
3
votes
2answers
540 views

In a ListPlot of LinearModelFit, plot error band

This is similar to this question. The fitted line can be plotted alongside with the data with this code: Show[ListPlot[data], Plot[lm[x], {x, 0, 5}]] I would ...
0
votes
1answer
288 views

Exporting tables of interpolating functions

A few weeks ago I asked a question about manipulating parameters in NDSolve (Looping with NDSolve?) , and received some very helpful advice about the manipulate environment; now I want to take the ...
2
votes
2answers
288 views

Fitting a variable using multiple equations

I would like to find the best fit of two variables for a number of approximate equations, such as: 1x+2y+2=7.04 2x+y+4=7.98 1.5x+1.5y-2=2.53 1.8x+3y-1=6.77 That ...
2
votes
1answer
86 views

Trouble with using a log10 function in NonlinearModelFit

I was wondering why won't mathematica give a result where the function is also Log10, instead it gives the ordinary Log. Is it ...
1
vote
1answer
315 views

Find polynomial equation for set of 3D data

data was given in columns in the order {y, x, z}, with y dependent on x, z ...