Regression analysis is the process of measuring and establishing a relationship between a dependent variable and one or more independent variables.

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Ridge Logistic Regression in R

I wrote code for Iterative Newton Raphson for logistic regression. Now I need to use the Ridge logistic regression. Any help to edit the code to have the coefficients after applying Ridge. And the ...
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78 views

Piecewise linear approximation of an experimental data curve. Knots position constrained

I need to fit a curve, obtained from experimental data, with a piecewise linear model (4 knots and therefore 3 lines). I tried using the MATLAB function ...
2
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1answer
59 views

fitting a non-linear curve

I have an equation: $\ddot{x}+(\delta+\epsilon\cos{t})x=0$ known as the Mathieu equation.The $\delta-\epsilon$ parameter space of this equation looks something like The red lines in this diagram ...
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1answer
67 views

Seeking a free symbolic regression software

Now that Formulize / Eureqa started charging $2500 a year for using it and having crippled the trial version, does anyone know of any replacements that can do similar things like find an equation ...
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0answers
28 views

linear solution of curve fitting on multiple linear functions differing by a multiplier

I am facing the following problem. I know nonlinear least squares can provide a solution but I am wondering if a linear way to solve this data fitting problem may exists. This is my input dataset: ...
6
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4answers
197 views

Surface fitting

I do not need a complete answer but just some advice. I have a sparse matrix of points in a volume. I know a surface passing by these points exists and this surface is mostly flat and relatively ...
2
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0answers
143 views

Polynomial Fitting with Least Squares using Numpy and Scipy

I am trying to fit data to a polynomial using Python - Numpy. The points, with lines sketched above them are as in the picture. I am trying to fit those points to a polynomial of 4. or 5. degree. ...
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1answer
77 views

what went wrong with my logistic regression implementation in c++?

I have implemented a simple logistic regression function with IRLS algorithm using the armadillo linear algebra libray ...
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1answer
61 views

Least Angle when $\textbf{A}^T\textbf{A}$ is singular

I'm teaching myself this regression stuff, so forgive me if this is a basic question. I can't seem to find a discussion of my particular problem. So I'm least-squares-ing this overdetermined system ...
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58 views

Why not use this simpler variant of Stepwise Regression?

In stepwise regression, you step predictor by predictor, each time selecting the one with the greatest correlation with the measurement, subtracting greedily to leave a residual with no correlation to ...
2
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2answers
1k views

Tikhonov regularization in the non-negative least square - NNLS (python:scipy)

I am working on a project that I need to add a regularization into the NNLS algorithm. Is there a way to add the Tikhonov regularization into the NNLS implementation of scipy [1]? [2] talks about it, ...
3
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2answers
201 views

Can the Levenberg-Marquardt algorithm be used for minimization and not fitting

Can the Levenberg-Marquardt algorithm be used for minimization and not fitting? Usually we input the derivative of the function we want to fit in the minimizer. Now if I assume I have an objective ...
2
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1answer
147 views

Some questions about MINPACK usage and messages

I am trying to use the nonlinear fitting routines of MINPACK for fitting a rather complicated equation of state to a set of experimental data. A subset of the data is fitted fairly well to a ...
2
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1answer
160 views

How to detect specific behavior in time series?

I was not quite sure what the right SE for this was, so I posted this also here on DSP. Please tell me which one to remove :) Problem statement I have a few hundred unrelated time series, say ...
3
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0answers
38 views

Partitioning Data for Multiple Regression Lines

We're all familiar with traditional least-squares method for constructing a straight line through a set of data points. The question is: suppose I show you a scatter plot which clearly is suggestive ...
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65 views

Differential equation - Model Fitting

My question is a quite simple one about statistics. I need to know the following thing. I have a differential equation from my model which I can solve. Now I can compare this solution with the ...
3
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2answers
56 views

Parameter Fitting: Need measure of data 'support' for a parameter solution

I am estimating parameters on a dataset that would, for the most part, result in a weakly constrained solution. The dataset however also contains a few more data points that make the solution ...
3
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1answer
250 views

Fitting one set of points to another by a rigid motion

I'm not really sure how to explain this problem clearly, so please bear with me. I have a basis of 3 orthonormal unit vectors and a position, a standard 4x4 transform matrix in computer graphics. ...
3
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1answer
42 views

How to obtain the minimum set of variables required in a model to produce accurate estimation?

I have a system which I assume is linear. I have a matrix $A$ of which each row is a coefficient of a unknown variables in vector $x$. I have vector $B$ which contains the result of each $Ax$. ...
3
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3answers
217 views

Averaging scattered data

I have multiple sets of measured data that can easily be visualized using a scatter plot (red and black points in the figure). If my measurements were perfect, the red and black points should lie on a ...
6
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4answers
762 views

parameters estimation

I have to estimate a parameter (K), but I don't know how I can do it. I think by a regression model (minimum least square?), but I'm not sure. The system is: ...
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0answers
83 views

Determining optimal number of clusters and Davies–Bouldin Index?

I'm trying to evaluate what is the right number of cluster needed for clusterize some data. I know that this is possible using Davies–Bouldin Index (DBI). To using DBI you have to compute it for any ...
3
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2answers
448 views

How to compute the optimal ridge regression model

I found R function ridge.cv very useful. I would like to implement the equivalent function in MATLAB. As a starting point, I used MATLAB function ...
3
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2answers
270 views

When fitting a Gaussian-like function, how does the amount of baseline datapoints affect the fit?

I am fitting a curve to some instrument data. The data is a pulse with a particular functional form, which starts from and returns to a constant (with noise) baseline level before and after the pulse. ...
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2answers
102 views

Matching Similar Items from a Set

I'm trying to match items. Given a set of $n$ items I can rank on a scale from 0 to 100 of how similar they are to one another. For instance, if item $n_1$ is milk and item $n_2$ is also milk, then ...
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2answers
596 views

Reporting curve-fit results in a scientific paper

(I hope this question fits this site; if not, accept my apologies). I ran a certain simulation, and got a time series y(t), t = 0, 1, ... 20. After trying some functions, I found that: ...
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1answer
156 views

Recover curves from noisy collection of points

Background: I'm trying to make a system that tracks a number of bubbles in a video I'm implementing the bubble detection in the single image case using the Circular Hough Transform. Due to ...
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2answers
213 views

Linear regression with quadratic constraints

What methods are suggested to solve problems of the form $\min || {A} x - y ||_k$, subject to $x^T P x \leq c$, and/or $x^T Q x = d$?
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2answers
76 views

What are all of the different methods for parameterizing an amino acid (or other small molecule)?

What are all of the different ways to derive the partial charges, van der Waals interactions, bond lengths, etc. of an amino acid (in other words, all of the parameters that could be used in a ...
2
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1answer
201 views

Polynomial Regression using Semidefinite Programming

I'm trying to design the frequency response function for a low-pass filter. I need the function to be polynomial and to fulfill the following constraints: the coefficients must sum to 1, the function ...
3
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1answer
258 views

Fitting a grid to an STM image

Suppose I have a scan from an STM image (very much like the things you see here). Suppose I have a simple square lattice with lattice parameter a. What I'd like to do is to numerically find the ...
8
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2answers
498 views

Kolmogorov–Smirnov test for multivariate data

I have a set of files consisting of randomly selected points from a dataset, each file belonging to a particular class. Each row in these files contains the coordinates in n-space of the point. I'd ...
4
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2answers
262 views

best way to optimize a function with linear/non-linear parameters

I am trying to fit some raw data using a function of the form $f(r) = \sum_{i=1}^{K} d_kS_k(n_k,\alpha_k,r)$ where $S_k(n_k,\alpha_k,r) = \frac{\alpha_k ^{n_k+3}}{(n_k+2)!}r^{n_k}\exp(-\alpha_kr)$ ...
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3answers
319 views

What should be the criteria for accepting/rejecting singular values?

I am solving a system using singular value decomposition. The singular values (before scaling) are: ...
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2answers
381 views

Quickly finding rough lines in sets of points

In a particular class of detector our data comes out as pairs of points in two dimensions, and we want to string these points into lines. The data is noisy, and is binned in one direction but not in ...
3
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2answers
406 views

Linear regression via SVD not producing best fit with escalating polynomial degree

I am using a basic singular value decomposition (via LAPACK) routine in FORTRAN to solve an overdetermined system in the form of $A\cdot X = B$ where $\mathrm{size}(A) = [m,n]$ with $m > n$. My ...