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

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0
votes
0answers
108 views

Non linear curve fit

I am trying to fit a non linear curve to my data which looks like following The code I am using is following. You can see I have six unknown variables ...
2
votes
1answer
60 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
votes
0answers
69 views

Can not understand the code to join points into line segments

I'm reading the CDF file from Making Formulas… for Everything in wolframalpha blog. It's hard for me to understand the In[17] code of function pointListToLines. I especially want to know what the use ...
2
votes
1answer
101 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 upon itself, loop, and so forth as for ...
3
votes
2answers
241 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
vote
0answers
86 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
174 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
vote
1answer
498 views

Fitting parameters of user defined function returning discrete values

So, I'm fairly new to Mathematica (apologies in advance for the noobiness), and I'm having some problems regarding fitting the parameters of a user defined function to data. I'll give a representative ...
1
vote
0answers
75 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
115 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
votes
0answers
78 views
0
votes
0answers
87 views

Curve fitting of a list

I have list obtained using an integrals. I want to obtain an analytical formula that fits my list using curve fitting. Please suggest a simple analytical structure that fits my curve. ...
0
votes
0answers
66 views

Using FindFit to return a list of possible best fits

Can I use some variant of FindFit that will return a list of the best fit and some worse fits, not just the best fit? This is for a function where the residual function can have several local ...
0
votes
1answer
120 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}, ...
6
votes
0answers
165 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 ...
1
vote
0answers
82 views

Findfit doesn't provide reasonable results when fitting a complex function [closed]

I am trying to fit some data using the function which contains two parameters (a, b) as described below. Hope to determine the a, b that best fit the data. My input is: ...
1
vote
0answers
76 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) ...
1
vote
0answers
124 views

Comparing two ways of fitting systems of ODEs to data

I'd like to ask you if you see any difference between the two following ways of estimating parameters. Given my system of ordinary differential equations that I want to use to find the values of all ...
2
votes
1answer
91 views

Struggling with FindFit

I'm trying to fit a sinusoidal wave to some numerical data. I can do it by hand using manipulate, so I know roughly the sort of parameter values that I should get back, but functions such as FindFit ...
6
votes
2answers
240 views

2D smoothing spline interpolation

Does Mathematica have 2D smoothing spline interpolation built in? I requires an interpolation method with smooth first derivatives and cubic bivariate splines fulfill this nicely. In python I would ...
13
votes
1answer
745 views

Curve fit based on minimal data

Inspired by the fantastic answers here and here, I would like to ask a questions along similar lines. I have 6 curve types that follow these rules: Type A: If point 1 is positive and point 2 is ...
5
votes
3answers
863 views

How can I obtain a smooth curve from my data but preserve two inversion points

I have a list of data points, {x, y}, my data. When I plot them, the curve is jagged. I want to smooth the curve and preserve the two sharp corners. This is a plot ...
14
votes
3answers
1k views

Fitting ellipse to 5 given points on the plane

Five points are required to define a unique ellipse. An ellipse has five degrees of freedom: the $x$ and $y$ coordinates of each focus, and the sum of the distance from each focus to a point on the ...
0
votes
1answer
501 views

Obtaining the envelope of an oscillating function and perform fitting

There is an elegant way to obtain the envelope of an oscillation function explained here http://mathematica.stackexchange.com/a/27854/15966 My question is how to modify the code below so I can fit ...
1
vote
0answers
53 views

How to regress negative log? [closed]

I made a regression using Linearmodelfit. The residual-fit plot showed that this was not a good approximation. Now I'm trying to use Nonlinearmodelfit. I assume my data to have a negative log look. ...
0
votes
0answers
84 views

Fitting a plane from a set of (x,y,z) values with uncertainties on 3 variables

I would like to fit a plane from a set of measurements (x,y,z) with uncertainties on the 3 variables. Currently I am using the command "LinearModelFit" that computes the best plane but I have a ...
1
vote
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
67 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
votes
1answer
81 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
417 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
vote
1answer
207 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
116 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
276 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
1k 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
232 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
votes
0answers
171 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
292 views

Fitting numerical model to experimental data

I have diffusion equation with the initial/boundary conditions: ...
2
votes
0answers
169 views

Power::infy: error using FindFit [closed]

I have a 2D data to fit (the Airy type pattern from diffraction of Gaussian beam on the circular aperture). Please see the attached picture. I was going to use a function like ...
3
votes
1answer
158 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
182 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
votes
5answers
2k views

Mathematica Implementations of the Random Forest algorithm

Is anyone aware of Mathematica use/implementation of Random Forest algorithm?
-1
votes
1answer
132 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
191 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
417 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
vote
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
158 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
736 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
vote
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 ...