# Tagged Questions

Questions on the use of Mathematica to construct models for approximating empirical data.

0answers
24 views

### Speed up evaluation of “ParameterErrors” from NonlinearModelFit? [on hold]

I am fitting my data to the analytic solution of a coupled differential equation with up to ten fit parameters. The fit itself takes 40 seconds however when I want to obtain the parameter errors, it ...
3answers
122 views

### smooth spline through airfoil coordinates

I am trying to produce a smooth spline curve through a set of airfoil coordinates. An example for the data I am trying to use is here, and I am reading the file like so to get rid of some extraneous ...
0answers
59 views

### Does Mathematica have built-in support for multivariate regression?

I know that LinearModelFit can generate a model of a single response variable as a function of a set in input variables. Does Mathematica provide support for ...
1answer
33 views

### Is it possible to get same answer from NonlinearModelFit with and without errors on data? - How to insert errors in NonlinearModelFit?

I want to use NonlinearModelFit with the following data. I tried it firstly without inserting any error bar. ...
3answers
121 views

### Automatically isolate the linear part of my data so that I can find its gradient?

I have some data plotted which is of bacterial growth curves, I have 96 sets of growth curves and I am wondering if there is a quick way to extract the straight line area of my growth curves in each ...
0answers
3 views

### Maximum Likelihood Approach for parameter estimation of multi response data, could you provide a tutorial? [migrated]

I was trying to fit the parameters a time dependent system coupled of ODES relate to a kinetic experiment with multi response data. example: A->B+H A+H->C+H A->D dcA(t)/dt=-k1Ca(t)-k2Ca(t)*Ch(t)-k3*Ca(...
2answers
198 views

### Curve fitting with this modified integrated log-normal function and extracting fitted?

The data to be fitted is for y vs x. We have y and x points. We do not have data for w. In fact, w variable is being varied during integration from 1e-9 to 100e-9. The fitting parameters are Ms,sigma,...
4answers
859 views

### Remove linear trend from data

I have a large data set with 150k lines and two data columns. I noticed that there is a linear trend, which I want to remove. So, I do the following: First, fit with a linear model: ...
1answer
89 views

### Importing Data to interpolation

I have an external file in extension XLS with looks as follows: This file can be obtained by the link below: Velocidade Angular With certainty this file is generating a list inappropriate for the ...
1answer
67 views

### Plotting a dataset and its fit dynamically

I have the dataset ...
3answers
241 views

### How to fit a Distribution to data that already looks like a distribution?

I have a set of data that is already ordered as a distribution. Here is a picture worth 999 words: I tried FindDistributionParameters, and ...
1answer
71 views

### getting a following error,large data points,desired output-best fit to expt. data sets

I am trying to carry out list operation but running into a following error I have large data sets(more than 0.2 million data points) and desired output will be a best fit (numerical data points ) to ...
1answer
83 views

### Knowing the functional form, how to find best-fit parameters and their uncertainties for a set of raw data in Mathematica 8?

I am trying to plot the best-fit curve (with known functional form but free parameters) passing through the following set of discrete data points which would take into account the size of error bars ...
4answers
99 views

### Using Manipulate to find best starting parameters to fit data

Often, curve fitting is very sensitive to starting values of parameters. It would be great, if I could to find such starting values of parameters "by hand" using Manipulate. So, I plot in ...
0answers
38 views

### Constrain a series of parameters while using FindMinimum

I'm working on fitting some experimental data using a model function that consists of sum of Lorentzians with width parameters A[1], ...
1answer
46 views

1answer
74 views

### Predicting the initial conditions of orbits inside a closed curve

I have a data file containing the four orbital element $(x,y,p_x,p_y)$ of a two-dimensional closed loop orbit. Note that the exact implicit equation of the orbit is not known. The plot of the 2D ...
1answer
137 views

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2answers
116 views

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0answers
87 views

### Softmax Regression Classification Algorithm

I'm following the Stanford Machine Learning course while simultaneously developing my Mathematica abilities. I'm having issues with my Softmax Classifier implementation (for ref, have a look at these ...
2answers
107 views

### Complex Fit, using NMinimize?

I'm having trouble fitting this complex data: ...
1answer
37 views

### NonlinearModelFit error: the function value is not a list of real numbers with dimensions {101} at {a,k,m0} = \ {1.,1.,1.} [closed]

So I'm trying to find a sigmoidal fit for my numerical solutions of these two ODEs but I keep getting an error and I don't know how to get around it. Here's my code: ...
2answers
652 views

### Fit a function to data so that fit is always equal or less than the data

I have a set of measurement data and I try to fit there a function (a Exp[b x] + c Exp[d x] - o). I have two problems: The fit function does not converge nor ...
1answer
88 views

### Data Fitting problem

I'm having this kind of data, and I know what possibly the equation is, i suspect this has a sine equation but the plot not really seems sinusoid. so what possibly the equation is so i can do the ...
2answers
123 views

### Nonlinear Fit sometimes does a good job and sometimes doesn't

So I'm trying to fit data, for all my data, the same fitting function can be used. Sometimes the fits actually FIT really well. Sometimes they just look completely random. Here's an example of it ...
0answers
61 views

### Solve equations involving summation expressions in Mathematica

I am trying to solve the simple linear regression equation analytically in Mathematica (not using builtin functions). I managed to calculate the gradient as follows f is loss function using RSS and ...
1answer
53 views

### Using LinearModelFit, how can I test the hypothesis $\beta=c$ with $c\neq 0$?

Assuming a simple linear model $y=x\beta+u$, is there a way to test the hypothesis $\beta=c$ with $c\neq 0$, using the LinearModelFit?
1answer
75 views

### FindFit works, NonlinearModelFit doesn't

I have a problem using NonlinearModelFit vs FindFit. Here is my code. ...
1answer
123 views

### How to fit this model [closed]

I have such data ...
2answers
65 views

### Fitting log-linear data

I am using NonlinearModelFit to extract the gradient of what appears to be linear data in a logplot: ...
3answers
3k views

### Fitting fractional complex data with NonlinearModelfit

I've difficulites with the NonlinearModelFit function. In principle Mathematica should be able to deal with complex data. E.g. if I define the following table <...
2answers
88 views

### best fitting crossing divides region plots with different background colors

We have two lists: ...
0answers
29 views

### data fit using second order PDE

I'm trying to find the parameter for second order PDE using data. i don't know what is the error of that, ...
2answers
84 views

### How to calculate unknown parameters

I have measurement data from impact test-test specimen location (Charpy). I am used by the plotting in excel this formula hyperbolical tan Y=y0+a*tanh[(t-x0)/b] ...