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

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13
votes
5answers
2k views

Fit image of mountain to gaussian

I want to detect the edges of an image of a mountain and then fit that to a gaussian. I am unsure about how to only get the mountain edge, rather than every single edge in the image. How do I ...
0
votes
2answers
62 views

Plotting plane from a matrix or data table

After weeks collecting data I've decided to pass my results through Wolfram Alpha and see what it gets. The results are amazingly useful, specially the plane generated by linear regression. It is ...
1
vote
2answers
72 views

Putting suitable constraints on the `Find` family of functions

Can any of the Find group of functions be used to get a good curve-fit for a range of data, if the value of $f(1)$ is known, and the value of $\lim_{n\rightarrow \...
2
votes
0answers
63 views

Algorithm used by Fit[]

Does anyone know what algorithm Mathematica's basic Fit[] function uses? Is it proprietary? I'm trying to do some pretty basic, linear, polynomial data fitting (...
4
votes
4answers
201 views

Fitting Coxian distribution to some data

I'm trying to fit a transformed (actually shifted to the right) Coxian distribution to some data ( if needed an example set is here Sim data ). I've tried a number of ways for this: ...
-2
votes
1answer
102 views

Computing least squares error [closed]

I have a mathematica subroutine setup that computes the least squares approximation as follows ...
4
votes
1answer
187 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 ...
0
votes
2answers
125 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. ...
5
votes
0answers
116 views

Ridge and lasso regression missing? [closed]

There is no implemented command to perform ridge or lasso regression? I couldn't find it in the documentation. Might be there are add-on packages I am not aware of.
28
votes
6answers
11k views

Estimate error on slope of linear regression given data with associated uncertainty

Given a set of data, is it possible to create a linear regression which has a slope error that takes into account the uncertainty of the data? This is for a high school class, and so the normal ...
3
votes
0answers
98 views

Writing a function to set up and solve the least squares problem

I have setup the explicit line equation for a given set of points using least-squares approximation and the knots computed below. I have tried extending the same code for use with an arbitrary degree, ...
1
vote
1answer
76 views

Paramter Scans and $\chi^2$ Test in Mathematica

Is there any in-built function or a recommended package that enables one to find, say, 10 Parameters, which are used as boundary conditions in NDSolve, that minimize $\chi^2$? ...
4
votes
1answer
94 views

Fitting real and imaginary parts of a function

I have an analytic form of a function G[w_] = -I*z0*w/(1 + I*z0*w*a) I know this function can be obtained (up to some overall normalization) from solving a ...
5
votes
1answer
191 views

How to fit data to a convolution equation

How to fit data to a convolution equation: ...
6
votes
1answer
108 views

Simulated Annealing, SearchPoints and InitialPoints options set at the same time

I have a function that needs to be minimized. Since the function depends on real-time data (which is fetched every few hours, and the function is redefined according to the new data), I have to run ...
1
vote
2answers
149 views

Problem fitting a exponential function to data points [closed]

finale edit: i found someone who solved my problem via matlab. therefore i wont try out the proposed solutions now, but wont delete my question in case someone might have use for the proposed ...
3
votes
2answers
184 views
1
vote
1answer
739 views

FindMinimum produces error message

I'm trying to solve a logistic regression problem using Mathematica -- more to improve my Mathematica skills than to solve the problem as I have already solved it using Octave. The problem I am ...
1
vote
0answers
49 views

NonLinearModelFit to a Function [closed]

I have a multiple dimension function that is fairly complicated. Instead of simply using Series to get a taylor series of the function, I would rather specify my ...
5
votes
1answer
114 views
1
vote
1answer
82 views

Faster way to test possible points-to-plane-fitting identity?

Summary: I want to confirm the three sum-defined quantities in https://github.com/barrycarter/bcapps/blob/master/STACK/planetest.m (also below) are identically zero for all values of n>=3. While ...
2
votes
0answers
101 views

LinearModelFit: Standard error or Standard error of the mean on the slope [closed]

UPDATED 02/14/16 Let me make this question clearer. Suppose each measurement that I make consists of three points, each with its own error governed by a normal distribution, on an XY plot. Obviously ...
1
vote
1answer
117 views

LinearModelFit: How to compute R-squared? [closed]

Is there a simple way to computed the R-Squared(adjusted and not adjusted), from the LinearModelFit? It has so many options, but none for the R-Squared, that I suspect there's a simple way to compute ...
1
vote
1answer
88 views

Fitting bivariate data using FindFit [closed]

I am trying to fit the following bivariate data set using the FindFit function: ...
3
votes
2answers
67 views
2
votes
1answer
133 views

Find a family of curves

I have a diagram with seven curves (each with a different parameter). My goal is to find a function for the family of curves (i.e. a single function not just for the seven parameters, but for all ...
0
votes
1answer
81 views

How can I calculate the root of any order of power series

How can I calculate the root of any order of power series with Mathematica. Here I insert every quantity by hand. But I want to give a, ...
1
vote
0answers
84 views

x and y axis nonlinear error fit possible? [duplicate]

I have a set of datapoints with x (position) errors as well as y (measurement) errors. Is there a way in Mathematica to fit a nonlinear function through this points, with weighting both, the x and y ...
13
votes
2answers
505 views

Fitting a curve to an image object: not a superellipse, not an egg curve.. what else?

I'm facing the problem of quantifying the morphology of objects with such a shape (nannoconids... they are fossils). One of the final goals is to produce a solid of revolution and compute volume/...
24
votes
3answers
839 views

Exponential fitting - isn't actually a BUG there?

There are many questions on this site about wrong exponential fitting in Mathematica but no one considers this well-known problem as a potential bug. Usually people suggest well-known workarounds ...
6
votes
1answer
331 views

Findfit does not find the best fit

I am working on a project that needs curve fitting. The experimental data should be fitted with a model that calculated with an integration equation. At first, I enter my experimental data ...
0
votes
1answer
96 views
2
votes
0answers
74 views

How to realize Global Fitting with shared parameters, same as OriginPro9.0? [closed]

I have an experimental data from Michelson interference and I can fit the envelope in OriginPro9.0 using Global Fitting with shared parameters. The figure by OriginPro9.0 is like this: However, I ...
8
votes
1answer
1k views

What exactly is “ParameterErrors” of NonlinearModelFit?

I am trying to get what I call a "$\chi^2$ fit". This means taking a function $f(x,p)$ of the variable $x$ with a parameter $p$ and finding the value of $p$ that minimizes the "distance" from a data ...
0
votes
2answers
104 views

Getting image data values with coordinates in circular region

I have a number of gray level images (600, with size: 2400x2400 pixel, small instance see above). In this image there is a circular region of interest. The aim is to fit a function to the gray value ...
2
votes
1answer
82 views

Fitting data in Log-Log scale

I want to fit my data from a txt file to a curve in log-log scale. What I tried to do was this: ...
4
votes
0answers
99 views

Fitting data with unique variable per measurement

Imagine we are in the following situation, we have a nonlinear system of functions $f$ with coördinates $x_i$, and unknown parameters $\delta_i$'s and $t$. Let this system be defined as, \begin{...
0
votes
0answers
35 views

How to calculate a required definition only once for each iteration of NonlinearModelFit [on hold]

This is my first post here. I've been using Mathematica for about 4 years now to analyze data, but am still very new and have no background in formal programming. This is the first question I couldn't ...
1
vote
1answer
98 views
0
votes
2answers
85 views

Find the linear combination of two functions to fit to a third

I have been trying to solve a simple enough problem, but I can't seem to find the proper method. The problem is given as, Find 0 < x < 1 for which, h(t) $\approx$ (1-x) f(t)+x g(t), where is ...
1
vote
0answers
60 views

Multivariate FindFormula? [closed]

I am using Mathematica Online and want to do FindFormula with two independent variables, but I cannot figure out if it's possible and if so what the syntax is. Here's my dataset: ...
1
vote
0answers
86 views

Fitting with constraints including the independent variable

I would like to write the following statement: data2fit = NonlinearModelFit[data2, {a Sqrt[b x + c] + d, b x + c > 0}, {a, b, c, d}, {x}] However, it returns ...
3
votes
2answers
241 views

Multiple regression curve fitting

I've got some data with 2 independent variables and 1 dependent variable I'm trying to fit a curve to. I'm really kind of a dummy with Mathematica except for the most basic things, so I looked ...
1
vote
0answers
82 views

Deriving ordinary least squares (OLS) in matrix form

How can I instruct Mathematica to derive the OLS in matrix form with respect to $\beta$ and obtain the result ${-2X}^{T}(y-X\beta)$? The matrices have the following dimensions: $y_{n \times 1}$, $X_{...
5
votes
0answers
118 views

Multivariate Adaptive Regression Splines (MARS) - Mathematica implementation?

Does anybody have or know of a Mathematica implementation of the Multivariate Adaptive Regression Splines (MARS) algorithm?
3
votes
1answer
123 views
3
votes
1answer
114 views

Why is TimeSeriesForecast linear?

When I use FinancialData with TimeSeriesForecast, the resulting graph is always linear and thus not very accurate. ...
0
votes
1answer
95 views

FindFit and log norm function

I'm trying to fit a function to data using FindFit, but I can't find a way to replace norm function RMSE with a RMSE in log space: ...
1
vote
0answers
73 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
0answers
494 views

Interpolating function as a model in Mathematica's procedures for fitting

Is it possible to use interpolating function with parameters as a model for NonLinearModelFit (and other integrated methods for fitting)? Similar question was ...