# Questions tagged [lars]

LARS stands for Least Angle Regression. It is a penalized estimation and feature selection technique for multiple regression.

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### What does lars return for lambda equal to zero when p is larger than n?

For the lasso problem $$\hat \beta(\lambda) = \underset{\beta \in \mathbb{R}^p}{\operatorname{argmin}}\|Y - X \beta\|_2^2 + \lambda \|\beta\|_1,$$ where $Y$ is $p \times 1$, $X$ is $n \times p$, it ...
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### Lars alphas_ results

Could any one explain how the results on alphas_ attribute in Lars model are calculated? In the definition: alphas_ is the maximum covariance (abs value) in each iteration. But when I look into ...
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### alpha and cv_alpha parameters in sklearn.linear_model.LarsCV

Can someone explain alpha and cv_alpha parameters in sklearn.linear_model.LarsCV? I am guessing that alphas refer to maximum correlation at any given step between one of the remaining explanatory ...
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### using the Lasso in sklearn [closed]

I am a beginner, and I am trying to use the Lasso to do some regression. I am looking specifically at the LassoLars module in sklearn. What I am really after is recovering the parameter weight vector ...
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### Cross-validated methods as a default

Scikit-learn ( http://scikit-learn.org/stable/modules/classes.html#module-sklearn.linear_model ) provide classes for Lasso, ElaticNet and Lars etc both with and without cross-validation. What are ...
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### Drawbacks of Lasso-lars combined with recursive feature elimination

During the model selection phase of my (regression) work I noticed that Lars with lasso modification performs way worse than any other model if combined with recursive feature elimination, both in ...
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### Stacking Lasso models

let say I have M subsets of independent variables and I want to use stack learner to predict dependent variable y. for each subset I use lasso method to get meta features (predictions). I have 2 ...
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### How to get the equiangular vector in p dimension linear space? Used in Least angle regression

Here I am reading the "Least angle regression" by Efron, 2004. https://projecteuclid.org/download/pdfview_1/euclid.aos/1083178935 , in page 413, he gives formula of equiangular vector of the linear ...
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### How can lasso CCA be solved using LARS?

According to paper By Sun, Ji an Ye; A Least Squares Formulation for Canonical Correlation Analysis http://www.machinelearning.org/archive/icml2008/papers/270.pdf CCA can be reformulated as a least ...
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### What is the rationale behind LARS-OLS hybrid, i.e. using OLS estimate on the variables chosen by LARS?

I need some help to understand the relationship between the ranking of the variables from the LARS algorithm and the use of OLS to estimate the final model chosen by the LARS. I understand that the ...
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### Classification with Least Angle (LARS)-type algorithm?

I am currently working on the LARS (Least Angle Regression) method. I know it is a regression method, but I wonder if, like LASSO or Ridge techniques (e.g. the package gmlnet in R), it can be ...
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### question in least angle regression paper [Efron et al. (2004)]

I am reading Efron et al. (2004), Ann. Statist., 32, 2, "Least angle regression". I have struggled with formula 5.19 for some days. It says the minimizing resolution of lasso occurs strictly inside ...
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### Inconsistent results for LASSO (glmnet package)

I am getting inconsistent results (coefficients and the mean cross-validated error) with the glmnet package in R. The data set has 33 variables and 250 observations. This is the sample output for the ...
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### Why under joint least squares direction is it possible for some coefficients to decrease in LARS regression? [duplicate]

I think I understand how LARS regression works. It basically adds features to the model when they are more correlated with the residuals than the current model. ...
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### Cross-validation and LASSO plot

I am not sure about some parts of the following plots: -- I do not understand what does the expression on x-axis means (first figure) and how to interpret that. -- What is the bars and the points in ...
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### LARS vs LASSO and Cross-validation

I would like to apply lars algorithm to some datadset. First, I fitted the model to the training set and then examined it on test set. My questions: 1- After I used cross validation "cv.lars" I ...
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### What is “step size” in LASSO regression?

I'm looking at this example for LASSO regression in R: http://machinelearningmastery.com/penalized-regression-in-r/. It ...
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### Cross-validated prediction error worse for LARS than ordinary linear regression

I am analysing microarray data in order to build a model for predicting cell proliferation (a continuous variable) based on gene expression (also a continuous variable). There are many more genes than ...
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### Computational complexity of the lasso (lars vs coordinate descent)

The lasso can be computed with the LARS or Coordinate Descent algorithm. What is their computational complexity and when one is quicker than the other?
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### LASSO regularisation parameter from LARS algorithm

In their seminal paper 'Least Angle Regression', Efron et al describe a simple modification of the LARS algorithm which allows to compute full LASSO regularisation paths. I have implemented this ...
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### How to imagine (visualize) the difference between LARS and Lasso

I'm reading the LARS paper. It turns out the solution path of LARS is quite similar with Lasso, and that paper has an explanation in section 3.1. An important fact ...
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### Using LASSO from lars (or glmnet) package in R for variable selection

Sorry if this question comes across a little basic. I am looking to use LASSO variable selection for a multiple linear regression model in R. I have 15 predictors, one of which is categorical(will ...
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### Least angle regression packages for R or MATLAB

I am looking for a Least Angle Regression (LAR) packages in R or MATLAB which can be used for classification problems. The only package that I currently know which fits this description is glmpath. ...
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### 'Forward Stagewise' option in LARS algorithm

Can anyone help me understand the forward stagewise part in the LARS algorithm? I was reading the R code and could not figure out what is ...
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### Max steps in lars

I don't know how many steps are necessary for lars() to select the variables till the algorithm proceeds to the saturated fit (especially using the ...
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### Constant signs of correlation in the active set in least angle regression

I am trying to comprehend the proof of the Least Angle Regression algorithm and I am stuck at certain points. I would appreciate any help that I can get. Let me set the stage: I am following the ...
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### LARS - LASSO with weights

I am interested in solving the following problem  \min_{\boldsymbol{\beta}} \left( \mathbf{y}-\mathbf{X}\boldsymbol{\beta} \right)^T W \left( \mathbf{y}-\mathbf{X}\boldsymbol{\beta} \right) + \...
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### Advantages of doing “double lasso” or performing lasso twice?

I once heard a method of using the lasso twice (like a double-lasso) where you perform lasso on the original set of variables, say S1, obtain a sparse set called S2, and then perform lasso again on ...
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### LASSO/LARS vs general to specific (GETS) method

I have been wondering, why are LASSO and LARS model selection methods so popular even though they are basically just variations of step-wise forward selection (and thus suffer from path dependency)? ...
I am using the least angle regression (LARS) to extract the most important predictors ($x_1, x_2,...,x_p$) for my response variable ($y$). I have seven predictors ($x_1,x_2,...,x_7$) for each ...