All Questions
Tagged with linearmodelfit or fitting
1,768 questions
1
vote
1
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164
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Fitting smooth monotonic function (low number of points, irregular grid)
I want to fit data in the hope of obtaining an estimate for other data points (i.e. a good guess for the last 4 variables as a function of the first).
Example data:
...
- 4,781
2
votes
1
answer
28
views
Fitting a free parameter by matching a an array with another array
I have the following problem that I can't figure out how to solve.
I have two measured signals, (data1 and data1), and their measured sum (datasummeasured). I have a theoretical description of how the ...
- 21
0
votes
1
answer
139
views
Using Manipulate for initial guess to nonlinear fitt, feed the result back to Manipulate (and repeat) for a general model with indexed parameters
I have been trying to put toghether a visual method to help fit experimental data with peaks. I have stumbled upon this answer which is very similar to where I got. But it is not sufficiently general ...
- 4,036
1
vote
2
answers
143
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Issues with Exp decay fitting using NonlinearModelFt
I am trying to fit a data set to an exponential decay function. The fit not only looks poor visually, but also the fitting parameters have high standard errors. It seems that the fit is getting stuck ...
- 1,225
0
votes
1
answer
90
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Fitting data to peaks visually with manipulate - how to compactly implement for many peaks
I am trying to create a visual aid for peak fitting. There should be a background profile and on top, I want to place peaks. So far, I am stuck with the following issue. For simplicity, I am using a ...
- 4,036
1
vote
1
answer
103
views
FitRegularization with a user function
I am trying to use FindFit with a user-defined function g[a] for FitRegularizaton as specified in the document. Say, I have parameters a1,a2,a3,a4 and define g[a] as
...
- 93
2
votes
0
answers
193
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How to approximate an exponential series?
Consider the following expression
$$
y_j= \sum_{k=0}^{L} \frac{e^{-\sum_{i=-k}^k(k-|i|)x_{j+i}}-e^{-\sum_{i=-k}^k(k+1-|i|)x_{j+i}}}{\sum_{i=-k}^k x_{j+i}}\tag{1}
$$
for $1\leq j \leq L$. Given smooth ...
- 4,953
3
votes
1
answer
344
views
SVD decomposition with optimization
Let's suppose there is a matrix A nxn, which will be decomposed into SVD:
where ui and vi are singular vectors composing matrix U and V. sigma is a vector that contains the eigenvalues. In ...
1
vote
2
answers
145
views
Parameter Estimation on ODE Using NMinimize (Least Squares Method)
I'm trying to estimate the parameters in this equation using this code:
...
- 11
3
votes
1
answer
115
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nonlinearfit with error message of "not valid" parameters
I am trying to fit a nonlinear function with four parameters to a dataset. It works, but standard errors are very high with the warning message "FittedModel::constr: The property values {...
- 1,225
0
votes
1
answer
153
views
Fitting data to a nonlinear model and avoiding warning
I have a complicated model and I want to fit it to my data.
I used NonlinearModelFit. The fit quality is very poor (P is infinitesimal) and it comes with a warning ...
1
vote
1
answer
261
views
Cannot solve a system of linear equations
I have four known functions, $u_i(x)$, and I suspect that all these four functions satisfy an operator, through a common force function, or at least a common force function type $(h(x)$, with some ...
- 619
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
1
vote
1
answer
89
views
Fitting a dataset while keeping the risk of overfitting low
I have the following dataset:
data = {{0, 1351.53}, {3, 1087.17}, {6, 1172.23}, {9, 1231.27}, {15, 1476.93}, {18, 1470.70}, {21, 1326.23}, {24, 316.80}}
which ...
user92576
0
votes
1
answer
79
views
Stability of linear fits
Let us consider the function $f(x)$ which has the expansion in fractional powers of $x$ near $x=0$ as shown below.
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- 93
0
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1
answer
68
views
How can an explicit formula for the envelope to an oscillatory damped function be obained?
So I have the function
...
7
votes
2
answers
407
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Measurement error propagation onto fitting-parameters
I have a dataset consisting of (t,y) Tuples, where each y has a known measurement error (standard deviation). I would like to fit a trapaze-function into the data and obtain the fitting paramaters and ...
- 73
0
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0
answers
77
views
The method to use for MultiNonlinearModelFit
I need to fit a complex function $f(z)$ of the form
f[z]=(p1[z]+p2[z]^(1/3)+p3[z]^(2/3))/(1+p5[z]^(5/6)+p6[z]^(19/6))
where all $p_i(z)$ are polynomials of degree ...
- 93
3
votes
2
answers
219
views
Fitting an exponential system
Consider the following system over a periodic array, where $1\leq j\leq n$,
$$
y_j= \sum_{k=0}^m \frac{e^{-\sum_{|i|\leq k}(k-|i|)x_{j+i}}-e^{-\sum_{|i|\leq k}(k+1-|i|)x_{j+i}}}{\sum_{|i|\leq k} x_{j+...
- 4,953
1
vote
1
answer
325
views
Forcing NonLinearModelFit to be positive
I've used the NonLinearModelFit function to get the fit for my data. I require the fit to to go through (0,0) (which I have ...
- 173
1
vote
1
answer
158
views
Finding a suitable form factor for a given set of conditions
I have the following Mathematica code:
...
- 2,953
0
votes
0
answers
73
views
Non-linear regression simulation
I have a sequence of data:
data = {{20, 291}, {21, 440}, {22, 571}, {23, 830}, {24, 1287}, {25, 1975}, {26, 2744}, {27, 4515}, {28, 5974}, {29, 7711}};
The data is ...
- 33
0
votes
2
answers
147
views
Plotting natural log equation in 3D plane
I have a natural log equation from excel and I need to plot it on 3D plane at a particular z(for example, z=1)
I would expect a vertical plane, but what I am getting is a horizontal plane.
This is ...
- 9
1
vote
1
answer
130
views
How to speedup calling the interpolation function? [duplicate]
Consider the following data:
...
- 5,963
0
votes
0
answers
71
views
Fit curve line doesn't extend over the correct domain
I'm trying to plot points as well as a non-linear fit function onto the same image. I used the command:
...
3
votes
0
answers
48
views
Performing Tobit Regression in Mathematica by Maximum LogLikelihood
I am trying to estimate a tobit model by maximum likelihood method in Mathematica. I can not find the build-in function. So I try to perform it manually.
Here is the log likelihood function of Tobit ...
- 51
0
votes
0
answers
59
views
Using FindFit for Approximation Fourier Series
I am expecting to have a list of discrete points, which I would like to approximate using Fourier's series, then plot Fourier series approximation alongside with discrete points, then plot terms of ...
- 43
2
votes
1
answer
96
views
'NonlinearModelFit' for SIR ODE model, and adding a penalty function (soft constraint)
This is a modification of the question Is it normal that adding constraints on the parameters of NonlinearModelFit increases execution time 100 times??
I want a program that fits a SIR model to ...
- 2,166
1
vote
1
answer
145
views
How to plot a curve with an experimental plot [closed]
There is an experimental curve in this paper : https://arxiv.org/pdf/1211.2616.pdf
( Fig. 21. ) I want to make a new plot of the experimental curve with my theoretical model curve. How to do so by ...
- 303
3
votes
1
answer
146
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Is it normal that adding constraints on the parameters of NonlinearModelFit increases execution time 100 times??
Normally, reducing the optimization domain by adding constraints should reduce the time of execution. In my case however, this puts the NonlinearModelFit in a coma. Without constraints, 8 seconds ...
- 2,166
0
votes
1
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327
views
Can constraints on the parameters be imposed in NonlinearModelFit? [closed]
Hi I cannot figure out this from the documentation of this command. For example, take one of the examples in the documentation, where I also added initial guesses for the parameters.
...
- 2,166
8
votes
2
answers
477
views
How to force fit of the data to exactly match one of its points?
Consider the following data:
...
- 5,963
0
votes
0
answers
108
views
Fitting NDSolve solution to data
I have a system of DDEs with 2 free parameters I solved with NDSolve, as you can see below
...
1
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0
answers
78
views
0
votes
1
answer
116
views
2
votes
1
answer
80
views
(Beginner question) How to solve large gradient region from experimental data?
I have a data like this.
data ={100, 103, 101, 105, 100, 80, 83, 70, 71, 60, 40, 43, 20, 22, 10, 5, -1, -3, -2, 0, 1, 4, 3, 8, 7, 4, 3, 1, 0, 1, 2, 10, 5, 2}
...
- 491
3
votes
1
answer
92
views
Nonlinear model Fit [closed]
I am trying to fit my data to the function:
a + (b*(c/2)^2)/((T - d)^2 + (c/2)^2)
I entered
nlm = NonlinearModelFit[data,
a + (b*(c/2)^2)/((T - d)^2 + (c/2)^2), {a, b, c, d}, T]
However it returned
[0....
- 33
2
votes
2
answers
142
views
Fourier series fit doesn't consider different local maxima of the data
I'm trying to appropriately fit a fourier model to experimental data. But the problem is that the resulting fit doesn't consider the varying local maxima of the data.
Here's the data:
...
0
votes
0
answers
74
views
How to fit piecewise functions with unknown domain?
Thank you for your comments, I will discribe the question in more detail.
I have a piecewise function as below and I'm looking for the parameters :...
- 1
0
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0
answers
125
views
0
votes
2
answers
49
views
How to archive scatterplot with randomly jittered x-values for visualization purpose? [closed]
I want to fit my data or just plot a figure with randomly jittered x-values like this:
Here I give an example:
...
- 38
11
votes
2
answers
330
views
Curve tracing for a given data set
I want to trace the curve for the given data set.
This is my code
...
- 2,730
2
votes
2
answers
132
views
How can I find an intermediate function between a set of functions?
I have 5 nonlinear functions, which are very complex and long. For this reason I will not include them here. But the plots of four of them are given here:
I am looking for some functionality which ...
- 619
1
vote
1
answer
207
views
Fitting data with results generated from a numerical model
I have system of 10 equations that I am solving to try and model some data collected. The model using the real world values doesn't produce the best result so I wanted to try and fit the model to the ...
- 324
7
votes
5
answers
407
views
3
votes
1
answer
167
views
Arbitrary shape cut into triangles and packed into rectangle of the same area [duplicate]
I've been trying to code this idea in lots of different approaches but I've reached a wall here. Mathematica isn't my strong suit and I've been unable to find a solution to the RegionMeasure error.
...
0
votes
1
answer
65
views
How to efficiently apply LinearModelFit for each column in a matrix
I have a source vector and a matrix of targets that I want to fit a linear model for. What is a more "Mathematica" way of doing this?. Here is my code to do it for the first column in target ...
- 117
0
votes
1
answer
121
views
Fitting parameter to match a dataset to another dataset
I am using a Module which calculates 3D-data based on 5 parameters and another input dataset.
I'd like to fit the result of this modul to another set of data.
Since my code became very long I will ...
1
vote
1
answer
166
views
Fitting an inverse power law [closed]
Is there any reasonably fast way of finding a function of the type
that best fits a given data, for some K and n? For example, the following data closely follows an inverse power law
...
- 4,953
1
vote
1
answer
393
views
Fitting data with Arrhenius Equation
I have the following data:
DataAZ400K = {{293, 1.98}, {313, 1.34}, {326, 1.58}, {344,
2.54}, {358, 3.8}, {373, 6.12}};
I want to fit this data with an ...
- 611