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Questions on the use of Mathematica to construct models for approximating empirical data.
2
votes
Fitting of 2d data points with a function considering scaling, rotation and translation
First change the function combinedTransformation to
combinedTransformation[{x_, y_}] =
{sx (prx (-Cos[theta]) + prx + pry Sin[theta]) + psx (-sx) + psx +
sx x Cos[theta] - sx y Sin[theta] + sx vecx …
3
votes
Accepted
Fit 3d data to a torus
Assuming that data is obtained from translated and/or rotated models
Clear[a, c]
p = {x, y, z};
P = {X, Y, Z};
Txyz = z^2 - a^2 + (c - (x^2 + y^2)^(1/2))^2 /. Thread[p -> RollPitchYawMatrix[{alpha, be …
1
vote
How to fit data to only half of a model
It seems that the best fit to pCD data is a gaussian bell as can be depicted. Hopelessly we don't have pCD data...
pIDmm = {{1, 4.}, {2, 4.}, {3, 0.}, {4, 5.}, {5, 4.}, {6, 8.}, {7, 12.}, {8, 11.}, { …
0
votes
Solving ODE System and Estimating Parameters with Experimental Data
Using the language resources
adata = {{0, 1}, {2, 0.88}, {6, .69}, {10, .53}, {20, .28}, {30, .15}, {50, .043}, {70, .012}, {90, 0}, {120, 0}, {150, 0}, {200, 0}};
bdata = {{0, 0}, {2, 0.12}, {6, .29 …
0
votes
ComplexFit fits only part of fit parameters
Fitting explicitly the real and imaginary parts.
mx[fr_, s_, t_] := s/(1 + t^2 fr^2)
my[fr_, s_, t_] := s t fr/(1 + t^2 fr^2)
frk = Transpose[data][[1]];
zk = Transpose[data][[2]];
zkr = Re[zk];
zki = …
0
votes
Fitting data using a parametric differential equation
The modified script below doesn't gives formal errors but keeps a lot of time processing before outputting some messages now linked to numerical problems.
eqns = {n'[t] == a L - b n[t]^2 - c n[t]^3 , …
4
votes
How to fit spline through points in $ \mathbb{R}^3$?
To eliminate noise in the data, it is best to perform a smoothing and not an interpolation. With the procedure that follows, three splines are adjusted one for each dimension, being that the degree of …
1
vote
Subtract peaks from curve
As a product of visual inspection, taking data from $\approx 80$ to $120$ and using the model
$$
f(a,b,\sigma_1,\sigma_2,x_1,x_2,x)=a e^{-\left(\frac{x-x_1}{\sigma_1}\right)^2}+b e^{-\left(\frac{x-x_2 …
2
votes
Fitting for constants
This is an extension for the excellent answer from @Ulrich Neumann considering
$$m\ddot x=-kx^{\alpha}-c\dot x-mg$$ instead of
$$m\ddot x=-kx-c\dot x-mg$$
tx = Map[{#[[1]], #[[2]]/100} &, data]
{tc, x …
3
votes
Accepted
How can I minimize a target function that has to solve differential equations numerically?
Clear[obj]
data2 = {{{0, 0.2025}, {2, 0.76}, {3, 1.28}, {4, 2.2}, {5, 2.75}, {6, 2.95}, {6.5, 3.055}}, {{0, 441.337}, {2, 400.435}, {3, 300.326}, {4, 219.348}, {5, 120.109}, {6, 50}, {6.5, 25}}, {{0, …
3
votes
Accepted
FindFit problem, some models work -- and some do not
With
xmin = Min@data[[All, 1]];
xmax = Max@data[[All, 1]];
ymin = Min@data[[All, 2]];
ymax = Max@data[[All, 2]];
After scaling
datanew = Table[{(data[[i, 1]] - xmin)/(xmax - xmin), (data[[i, 2]] - ym …
2
votes
Determination of radius based on data points
A = Uncompress[FromCharacterCode[
Flatten[ImageData[Import["https://i.sstatic.net/s6rlR.png"],
"Byte"]]]];
B = Uncompress[FromCharacterCode[
Flatten[ImageData[Import["https://i.sstatic.net/jylyd.pn …
3
votes
Accepted
Optimizing an ODE fitting algorithm with interpolated data
Another way to do the fitting.
1 - We will using a custom-made second order interpolation as giving in f[t]. … This facilitates an undesirable over-fitting. …
1
vote
Accepted
Fitting delay differential equations (DDE)
Introducing few modifications in the actual script, we found using MATHEMATICA version 12.0.0 running under Linux,
Follows the script
fitness[a00_?NumberQ, c00_?NumberQ, d00_?NumberQ, s0_?NumberQ, b …