Questions tagged [curve-fitting]

For questions about determining parameters for particular functional form based on set of given data points. These points may be the exact values generated from some underlying function or possibly have some additional noise component.

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Pade-like approximation, but force poles to be negative

Are there techniques to form a Pade approximation (or Pade-like approximation), except force the poles of the rational function to be negative? I am trying to use Pade approximations to extrapolate a ...
Nick Alger's user avatar
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3 votes
0 answers
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Least-squares fit of explicit parabolic sheet to data points

For a given set of data points $$\{(x_i, y_i, z_i)\}$$ there exists some $$f_{ABC}(x,y)=Ax^2+Bxy+Cy^2$$ that minimizes $$\sum_i(f_{ABC}(x_i,y_i)-z_i)^2$$ $A$, $B$, and $C$ can be found quickly ...
Museful's user avatar
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2 votes
0 answers
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Good 3D surface fits for multiscale oscillatory surfaces

I have a 3D surface in $x$, $y$, and $z$. where $z$ is a function of $x$ and $y$ and my points are on a structured grid in $x$ and $y$. My function $z$ is highly oscillatory and irregular with ...
EMP's user avatar
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2 votes
0 answers
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Inverted value is not consistent with expectation

We have a group of observations $$y = f(x_1, x_2, x_3) \enspace .$$ We have also a forward model $y = f(x_1, x_2)$. The forward model does not include $x_3$ because $x_3$ might include dozens of ...
Ting Yang's user avatar
2 votes
0 answers
194 views

Produce one smooth curve on one triangle mesh

I hope to get one smooth curve on one triangle mesh. I get one path on the mesh at first. The path consists of vertices of the mesh. I can see the path from the image below. Each one green dot ...
Jogging Song's user avatar
1 vote
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Given a set of 1d-points, find the most probable periodicity that models the points (with possible omissions) as equidistant occurences

I try to detect interference fringes in a bunch of pictures. I projected on one axis, and I was able to detekt the peaks that indicate one of the fringes. So now I'm having a list with points (e.g. $(...
Quantumwhisp's user avatar
1 vote
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Fitting data with a Voigt function

I have some data, (xrd data), that I would like peak fit with a pseudo-Voigt function, a combination of a Gaussian and a Lorentzian function. These are the functions $G(x) = I \exp\left( -\frac{4\ln(2)...
Peter's user avatar
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1 vote
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Fitting a multivariate PDE (using Java)

I'm doing simulations of 2 coupled PDE's with Comsol Multiphysics. I want to fit some data (using the Application method, whose language is Java) to those simulations. In order to answer my question ...
J.A's user avatar
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1 vote
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Error on the fit parameters when several good fits exist

I am using the reduced chi-squared statistic to determine the goodness of fit. I run several simulations and determine that a parameter 'p' has a certain range of values that all give values between 0....
Sameeresque's user avatar
1 vote
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Fit constant term in LM algorithm

I'm using the Levenberg-Marquardt algorithm to fit my data with a Gaussian function: $$ f(x)=a\cdot e^{-\frac{(x-c)^2}{2\sigma^2}}+f_0 $$ $a$, $c$, $\sigma$ and $f_0$ are the fitting parameters. The ...
GoGoLander's user avatar
1 vote
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141 views

How to curve fit an unknown function?

I have data which can be described by $y=f(x,z)$ where $z$ varies from 170 ~ 154. Now values given by $ks$ are known sample values that equals value given in the table header, $uks$ are unknown ...
nxkryptor's user avatar
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1 vote
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Piecewise linear approximation of an experimental data curve. Knots position constrained

I need to fit a curve, obtained from experimental data, with a piecewise linear model (4 knots and therefore 3 lines). I tried using the MATLAB function ...
Rhei's user avatar
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Computing autocorrelation of scalar values

I obtained a list of $r^2_{end-to-end}$ from a Monte Carlo simulation of polymer movement. ...
user366312's user avatar
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biexponential fits where exponents are very similar to each other but different than best monoexponential fit

I have some data which consists of an exponential process in time convolved with a gating function. I am fitting the underlying exponential using the least squares method. (I also have experimental ...
QMStatMech's user avatar
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527 views

Curve fitting using a piecewise polynomial

I am trying to fit a piecewise polynomial function Code: ...
Natasha's user avatar
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43 views

I would like to fit a data to integral type model but cannot figure it how?

I have cumulative data for concentration versus time. I would like to fit the following model to the data: $$\frac{1}{\Gamma(n) \bar{t}}\int_{0}^{\frac{n t}{\bar{t}}}z^{n-1} e^{-z}dz$$ $n$ and $\bar{...
isar charmchi's user avatar
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Fit exponential convergence

I'm working with a numerical algorithm whose output $y$ asymptotically approaches a certain unknown value $a$. I expect an exponential convergence, i.e. the data $y$ given by my algorithm should be ...
AndreaPaco's user avatar
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148 views

1D fit on a surface in matlab

I have a problem fitting a $N\times N$ ($32\times 32$ in this case) matrix in Matlab. Here is the deal I have this image, and I want to create 1 dimensional fit between the points and then be able ...
Mike's user avatar
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