All Questions
35 questions
1
vote
1
answer
116
views
When using FindFit to fit a large dataset with multiple sine functions, a step size error occur
My dataset looks like
datatandA = Import["dataForQuestionFindFit20240528.csv"];
ListPlot[datatandA]
and the corresponding FFT spectrum looks like
...
- 495
1
vote
1
answer
359
views
Fitting delay differential equations (DDE)
I have the following differential equations:
$$S'(t) = 0.31 S(t) \Big( 1 - \frac{S(t)}{6.19} \Big)- \frac{a}{1 + B(t)} S(t),$$
$$B'(t) = c (1 - B(t)) - d B(t) S(t) - 3 c (1 - B(t - 18)),$$
where $B(t -...
user95418
1
vote
0
answers
472
views
How to include impulses in differential equations?
I have two coupled differential equations as follows:
$$S'(t) = - \frac{a}{1 + B(t)} S(t),$$
$$B'(t) = \frac{c}{1 + S(t)} B(t) (1 - B(t)) - d B^2(t) \Big( \frac{1 - B(t)}{B(t)} \Big)^n,$$
where $a$, $...
user95418
0
votes
1
answer
214
views
Using ParametricNDSolveValue and MultiNonlinearModelFit to fit an ODE system to datasets
I asked a question here about fitting an ODE system to given datasets. The great answer of @ydd solved the problem nicely. In the mentioned answer, the initial values are taken as the initial points ...
user95418
4
votes
2
answers
447
views
Modeling experimental data with differential equations
I have the following two sets of experimental data, which show the dependencies of two quantities, namely, $S$ and $B$, on time ($0$ h, $3$ h, $6$ h, $9$ h, $15$ h, $18$ h, $21$ h, and $24$ h):
...
user95418
0
votes
1
answer
63
views
How to properly expand a list with certain numerical elements?
There is a list with 19 elements ...
- 1,893
4
votes
4
answers
338
views
Simultaneous nonlinear fitting of two datasets to two trial functions with shared parameters
I'm relatively new to mathematica and stack exchange.
Problem
Generally my problem concerns finding a simultaneous fit of multiple functions to multiple datasets with shared parameters. I have looked ...
- 317
1
vote
1
answer
388
views
How to get a function out of NDSolve
I solved a function using NDSolve and got a result. I also have a plot of the function.
Could someone point me in the right direction how I can print the explicit data points and/or generate a fit ...
- 97
4
votes
1
answer
258
views
Fit: Experimental`NumericalFunction error when fitting a black-box function
Bug appearing in at least 12.0.0 and 12.3.1
I'm trying some multidimensional Chebyshev fits. First, define a wrapper to prevent premature symbolic evaluation (I don't want a power series result):
<...
- 14k
2
votes
2
answers
141
views
Can I impose some a priori constraints on a distribution found by SmoothKernelDistribution?
I use SmoothKernelDistribution (with no options and a single argument — a list of values) to get an approximate reconstruction of a continuous distribution based on ...
- 7,333
3
votes
2
answers
2k
views
How to merge two or more curves smoothly?
I have plotted three curves. For each range of $x$, one of those curves is true. On the other hand, finally, the result must be a unified curve. Is there any command to unify these three curves?
...
- 703
0
votes
1
answer
118
views
How can I define the following function for arbitray values of the arguments?
Consider the following function
a[m_, l_] = 1/Log[m/l];
with this function I define
...
- 563
1
vote
2
answers
532
views
Getting error General::munfl from NonlinearModelFit [duplicate]
I am trying to fit data to a sum of Gaussians.
This data is found in a file called lpeff.txt. So I write the following code:
...
- 11
3
votes
1
answer
387
views
Approximating decay rate of an amplitude and frequency of an oscillating function
I have an InterpolatingFunction constructed from a discrete set of values obtained by numerical methods. Let's denote it $f(x)$. The function demonstrates an ...
- 7,333
0
votes
0
answers
212
views
Energy minimization
I am trying to fit some experimental data, and for that I need to solve the following problems:
1) Minimize the energy of a system of the following form:
(Not a code, but editor require it to be so)
...
- 13
3
votes
1
answer
169
views
Increasing the accuracy of the fit when using LinearModelFit
Question: is it possible to increase the accuracy of the BestFit property for LinearModelFit?
I have code that uses ...
- 163
2
votes
2
answers
455
views
Fitting Asymptotic Ansatz to Numerical solution of Differential equation
Consider the following differential equation: $$ \frac{1}{a} \frac{dy}{dx} = -\frac{1}{y} e^{-\frac{1}{y}} $$ with initial condition $y(0) = 1$ and $a = 10$. This is easily solved numerically with $...
- 779
10
votes
2
answers
1k
views
Fitting experimental data by using ParametricNDSolveValue and NonlinearModelFit
I am a newcomer to Mathematica.
Basically I just want to fit the data (enzyme kinetic data) shown below to a system of odes' by using NonlinearModelFit. The data, an 101x2 array, contains time in the ...
- 101
1
vote
0
answers
99
views
Fitting Data to Restriction of Known Function?
So I have a list of data points living in the $(x,y)$-plane. These data points come from a complicated curve in this plane whose exact form is not known! I am hoping to evaluate the Weirstrass-$\wp$ ...
- 1,337
5
votes
3
answers
528
views
Fitting data with several peaks
I am trying to fit a set of data with a specific model using the following code.
As the figure shows, the fitting procedure is not great. First there is an error message, and as is obvious the fitting ...
- 3,268
25
votes
3
answers
1k
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 ...
- 62.3k
0
votes
1
answer
132
views
1
vote
1
answer
172
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 $\chi^2$?
...
- 950
4
votes
3
answers
666
views
Use NMinimize instead of FindFit for constrained search (of coefficients)
(My problem is more complex, but let us formulate it through this example)
I am trying to find the best polynomial approximation to the following function
...
- 671
3
votes
1
answer
722
views
Non-linear curve fit problem
I am having a problem with making a fit to data in Mathematica, which may involve my understanding of the methods available.
I am trying to fit the derivative of a Frota function (which is a Single ...
- 31
4
votes
2
answers
472
views
How to use Evaluation Monitor in conjunction with NonlineaModelFit?
I am trying to find out how many function, gradient and hessian evaluations are made when i run NonlinearModelFit for example in this case
...
- 41
0
votes
1
answer
234
views
How to adjust excel data for NonlinearModelFit?
I'm really new to Mathematica and I'm facing a problem and would really appreciate some help! Maybe my question is similar to one described in How to fit 3 data sets to a model of 4 differential ...
- 21
4
votes
1
answer
396
views
FindFit runs extremely slow for my Function,how do I optimize this?
My function is the first order Bessel Function, and I am basically just trying to get this to fit in a way that does not take forever.
I define the function as follows, (it seems to work faster if I ...
- 43
1
vote
1
answer
1k
views
Fitting data with inclusion of constraints
How do I find a fit for the dataS (see below) with the constraint that the parameter np
is an integer, and that the parameters la+lc = 100. A weak attempt at this is provided below for a specific ...
- 3,268
1
vote
1
answer
331
views
Find Numerical Derivatives (With Errors) given some data
I have a question. Suposse I have some data with their respective errors:
...
2
votes
1
answer
1k
views
Problem with Covariance Matrix Output in NonlinearModelFit
I am running NonlinearModelFit based off of some simulated data and trying to fit to a function with more than one parameter. Eventually, I would like to fit to 5 ...
- 33
33
votes
2
answers
8k
views
How to fit 3 data sets to a model of 4 differential equations?
I'm a biologist and a newbie in Mathematica. I want to fit three data sets to a model consisting of four differential equations and 10 parameters. I want to find the parameters best fitting to my ...
- 333
17
votes
3
answers
6k
views
Finding a fit to a multi-dimensioned function
I have a model function $f:\mathbb{R}^2\rightarrow\mathbb{R}^2$, and a bunch of data points for which I'd like Mathematica to fit for me. Unfortunately FindFit ...
- 14.3k
4
votes
3
answers
1k
views
Output of NonlinearModelFit differs from the correct result
I'm having a bad time dealing with the NonlinearModelFit in Mathematica 8, since the result given is a bit imprecise. An example is given on potential regression, ...
15
votes
2
answers
2k
views
Is it possible to use the LevenbergMarquardt algorithm for fitting a black-box residual function?
I have a black-box multiargument multiparametric function of the type SRD[dataPoint_List,params_List] which accepts experimental data along with the parameters of ...
- 62.3k