Questions tagged [fitting]
Questions on the use of Mathematica to construct models for approximating empirical data.
1,444
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How to Fit This Chemical Experiment Data with such a Complicated Theoretical Model?
I am fitting data on an experiment of potentiometric titration that uses alkali to titrate weak acid in analytical chemistry.
Here is the data:
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0
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1answer
30 views
Linear regression: confidence interval of the average of 10 slopes, error of propagation and error of the mean
I have 10 regression slopes in one group, each slope has its associated standard error. Now I want to find the average slope of this group and the associated standard error which will be used to find ...
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0answers
29 views
Simplify function to find rate constants
I have a function to calculate rate constants using nonlinear least square modeling from a 2011 paper by Jia et al. https://www.cell.com/cell/fulltext/S0092-8674(11)00536-8?_returnURL=https%3A%2F%...
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2answers
88 views
Fitting data to equation with one fitting parameter
If I have the following data (x value is composition and y value is temperature):
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1answer
64 views
2
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1answer
39 views
NonlinearModelFit a custom function - getting wrong fit parameters and huge std
Im trying to Fit some measured Data, but the fitted parameters which the FindFit[] Ffunction is returning are completly off.
I have the following Data depending on the Temperature
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2answers
62 views
Fittind data with shifted Chebyshev polynomials
I am trying to fit data from a simulation to a particular class of polynomials, according to least squares approach.
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1answer
123 views
Find a “ridge line” from a set of irregularly spaced points
I'm solvind a slope stability problem whith the finite element method. As an output I get the square root of the second deviatoric invariant of the plastic deformation, which indicates the failure ...
1
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1answer
82 views
Exponential Decay fit and printed parameters with integer data [closed]
Problem:
I'm trying to plot an exponential decay curve on a set of integer data, and print the various parameters and their uncertainties on the plot itself. Having adapted code from another question, ...
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2answers
63 views
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How does NonlinearModelFit work? [closed]
Suppose I have a model $ f (x) $ with some free parameters $ a, b $ and I want to fit my model to a data set called Dx.
How does NonlinearModelFit find the value of ...
2
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1answer
57 views
Best fit curve for a list of data
I am kinda new to Mathematica and I have some basic questions.
I need to find the best fit curve for a set of data.
Here's the data:
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0answers
27 views
NMinimize sum of several fitted results
I have 10 data sets and assume them a same parameter, offset in the CorrelationFit function. I would like to minimize the ...
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1answer
28 views
How to convert element's Table to List / Array to make an independent multivariable fit?
I would like to make an independent multivariable fit, but I have problems using a Table that I generated. I can´t use their elements because it isn´t in a list or a rectangular array.
Using Table[ ] ...
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2answers
233 views
Fit ellipse to a arbitrary 2D image to extract centroid, orientation, major, minor axis
I am wondering if there is an easy way to fit an ellipse into an arbitrary 2D image quickly, so its centroid, orientation, major, and minor axis length can directly be extracted. In MATLAB, this can ...
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2answers
266 views
How to fit a curve in a picture with an equation?
For a curve taken from a picture, is there any method to fit it with an equation if it appears to be some standard curve?
For example, in the following picture, the curve looks like an ellipse or a ...
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57 views
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31 views
How to evaluate fit at a fixed point
How can I evaluate the result of Fit applied to the data used in the example code below
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0answers
24 views
ParameterTable from NonlinearModelFit returns error messages
I am doing some nonlinear regression using NonlinearModelFit function. Here in the code I am currently working on.
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1answer
75 views
Plot Styling Errors (PlotLabel, PlotTheme, Inset not appearing)
Question:
I'm trying to pull together a graph with labelled axes, a title, and an inset box with information relating to the plot such as the y-intercept (A in this code) and it's uncertainty. However,...
2
votes
1answer
100 views
Finding Chi^2 of a Non-Linear Fit Model
Question:
I have some data, with a y=Ae^(-kt) model applied (It's a radioactive decay), thanks to answers on another question, the model is applied and returns the ...
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1answer
58 views
How to show all global minimizers?
This is a follow-up to this question and I'm aware of this question for the local minimizers case.
Consider, for $0\leq \epsilon\leq 1$ and $0<q,p<1$, the function
$$
\begin{align}
f(\...
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1answer
91 views
Mathematica Linear Regression [closed]
How do I create a user-defined function for linear regression without using the built in function. Essentially doing the steps one by one
3
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0answers
73 views
Finding multiple minimizers
Is it possible to find all (or as many as possible) minimizers of a given function? For example, minimizing the function $\cos(\pi(p-q))+\cos(\pi(q+p))$ for $-3\leq p,q\leq 3 $ can be done using ...
2
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1answer
32 views
2
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1answer
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Limit variable in NonLinearModel Fit to a list
I'm attempting to constrain the values of some of the model fit variables to a list of defined numbers. Here are a sample dataset and model.
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2
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1answer
56 views
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Multivariate AR process model fit
Is there a function in Mathematica that allows me to fit a VAR model with 4 variables?
Let's say I have the following simulated data:
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0
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1answer
39 views
Confidence interval for variance in fit
When using (Non)LinearModelFit you can get estimates for all parameters and for the variance of the fit and confidence intervals for parameters, but what about a confidence interval for the variance?
<...
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67 views
How do I remove a singularity that appears when I make a fit to my data?
I am trying to fit a complex algebraic function to a data set Data, which is basically a Lorentzian. The problem I am facing that while fitting there exists an infinity. Could you help me to get rid ...
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0answers
31 views
Fitting nonlinear model to intensity plot with Gaussian weights?
I am trying to fit my model $\omega(\vec{k})$ to the following experimental data to extract three parameters $J_x$, $J_y$, and $J_z$. The data that I am trying to fit to is:
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32 views
Nonlinear model fitting constraint problem
I have been having a great deal of difficulty understanding how to properly use the "NonlinearModelFit" functionality in Mathematica. I have scoured the documentation and online videos ...
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56 views
Constraint of a variable with an expression in nonlinear model fitting - independent variable constraint?
I am attempting to fit a set of experimental binding data:
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0answers
24 views
NArgMin with Root functions
I'm trying to minimize an error function sumt to find some parameters S, s0, si :
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30 views
Removing Irregular Transient Spike from Linear data trend
The x-y data that is being analyzed generates a linear relationship (y=mx+b) when in steady-state flow. NON-REGULAR transients are often introduced into the system. These transients prevent the ...
4
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2answers
148 views
Applying an exponential decay fit with uncertainties
I have some data from a radioactive decay experiment that I'm trying to fit an exponential decay curve on that will take account of the uncertainties on the data, and then ideally return the data for ...
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0answers
38 views
Fit data to a model of two-variable differential equations
I am trying to fit some data to the solution of a differential equation. I am using ParametricNDSolve to create a model which should fit the data using ...
1
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0answers
78 views
NonlinearModelFit with two-dimensional input to two-dimensional output
I want to estimate a nonlinear mapping from two-dimensional input positions to two-dimensional output positions. (Think of this as a nonlinear distortion of an image. Once I get the estimated ...
0
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1answer
75 views
Fitting 3D data with a nonlinear model
I am trying to fit a model to an intensity map to extract three values for the parameters of my model $J_x, J_y, J_z$. Currently, I am running into the issue where I can extract values for these three ...
1
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1answer
104 views
How can I minimize a target function that has to solve differential equations numerically?
My problem is to minimize a target function with differential equations in it.
The target function is
$$\min \mathrm{J}\left( p \right) =\sum_{i=1}^5{|x_i\left( p \right) -y_i|},$$
where $x_i(p)$ are ...
0
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1answer
56 views
Regression of a set of (2-element) vectors on another set of (2-element) vectors
As a trivial example, here are two vectors:
f = {{1, 1}, {2, 2}, {3, 3}, {4, 4}}
s = {{-1, 2}, {-2, 4}, {-3, 6}, {-4, 8}}
It is instantly clear (apart from my ...
0
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1answer
56 views
Fit and Data in (1/x,-Log[y])-Scale
I have data as a list of xy-pairs, but have to plot it in {1/(x), -Log[y]} space. I am also making a fit to the data, so I used the raw data for my fit and I used <...
2
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2answers
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ProbitModelFit is causing kernel crashes in Mathematica 12.0
Mathematica 12.0
I am running ProbitModelFit on a small data set (~130 rows). Intermittently, the function causes a kernel crash. I am curious if anyone else is ...
0
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1answer
36 views
finding FWHM of a dataset with unknown mathematical equation
I have a dataset. I have plotted using "Listloglinearplot". Now I need to find the FWHM (full width half maxima) of the same, However I dont know which mathematical eqution describes best to ...
0
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1answer
44 views
Find Fit error 4P logistic
I am trying to fit a four parameter logistic curve to my data set. I have the estimated values for each coefficint, but it says the jacobian is not a matrix...
Here is my data:
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1answer
86 views
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1answer
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Gaussian fit with asymmetric background
I have to fit this peak (which seems to be a double gaussian from other experiments) to find the peak position of the one at around 2.43 eV.
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