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.
18
questions with no upvoted or accepted answers
4
votes
0
answers
97
views
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 ...
3
votes
0
answers
58
views
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 ...
2
votes
0
answers
47
views
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 ...
2
votes
0
answers
57
views
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 ...
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 ...
1
vote
0
answers
19
views
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. $(...
1
vote
0
answers
197
views
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)...
1
vote
0
answers
44
views
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 ...
1
vote
0
answers
18
views
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....
1
vote
0
answers
55
views
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 ...
1
vote
0
answers
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 ...
1
vote
0
answers
2k
views
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
...
0
votes
0
answers
24
views
Computing autocorrelation of scalar values
I obtained a list of $r^2_{end-to-end}$ from a Monte Carlo simulation of polymer movement.
...
0
votes
0
answers
47
views
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 ...
0
votes
0
answers
527
views
Curve fitting using a piecewise polynomial
I am trying to fit a piecewise polynomial function
Code:
...
0
votes
0
answers
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{...
0
votes
0
answers
64
views
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 ...
0
votes
0
answers
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 ...