Questions tagged [sparse]

A sparse matrix is a matrix where many of the elements are zeros. The tag can also be used for sparsity in other contexts, such as regression models with sparsity, or the "bet on sparsity"-principle.

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Enforcing sparsity constraints that make use of spatial contiguity

I have a deep learning network that outputs grayscale image reconstructions. In addition to good reconstruction performance (measured through mean squared error or some other measure like psnr), I ...
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What is the appropriate metric for determining distance / dissimilarity of sparse, high dimensional data in PCA space?

I'm working with scRNA-seq data (~96% sparse, high dimensional), and am trying to determine distances between the cells in PCA space - NOT for the specific purpose of clustering. The principal ...
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29 views

L1 feature selection followed by exhaustive search

I'm working with a group on an ML project and one of the team members has proposed using L1 to reduce the feature space and then apply an exhaustive search with the reduced feature set. In each step, ...
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Custom Tensorflow v2.x Optimizer with Sparse update support

I am trying to contribute to tensorflow v2. I am done with _resource_apply_dense but i am struggling with _resource_apply_sparse. There are multiple ways to handle but there is no proper discussion ...
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15 views

NLP multiclass classification with many sparse classes

I am attempting to use natural language processing to geocode "addresses". The address is the result of a write-in of a survey where the respondent is instructed to give their city, state, ...
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86 views

Estimation of Sparse Panel Data

There are 1000 students and 100 teachers. Each teacher is given the answer scripts of randomly selected 100 students. So in total 10,000 answer scripts are judged. Now this is sort of panel data, but ...
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110 views

What is a Dirac distribution on a hyperplane?

I'm trying to understand message passing for compressed sensing. I came acrross this distribution: As the title suggests, how does this distribution look like? I know the first products term in the ...
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Sparsity-inducing priors for non-negative random variables

Which priors could be used for inducing sparsity on a random variable with non-negativity constraints?
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13 views

Distance Metric for Sparse Data

I'm aware of similar questions like Distance metric for categorical and numerical data. I have a very sparse matrix and I want to a distance metric to find the most different items. Would performing ...
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geometric interpretation of SAFE rule for LASSO

El Ghaoui et al. showed that in the solution for the LASSO optimization problem $$ \hat{\beta} = \underset{\beta \in \mathbb{R}^p}{\operatorname{argmin}} \frac{1}{2} ||\boldsymbol{y} - \boldsymbol{X}\...
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Is K-medoids / partitioning around medoids (PAM) appropriate for clustering data with many zero values?

I need to cluster a matrix which contains zero values. I am clustering three separate sets of 24 values. The first two are non-zero and represent hourly ambient temperature (in K) and electrical ...
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36 views

How to train a Neural Network on sparse data?

I am trying to train a sequence model to extract specific substrings. I am working on extremely sparse text data (Sparsity ~ 0.03%, <1000 examples). After training for 500 epochs, the performance ...
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Calculating similarities between two populations using embeddings

I would like to find items from population B that are most similar to an item from population A. I have the following set up: Two sparse datasets where each row is an item (treat row index as item ID)...
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66 views

Power simulation on glmer.nb gave strange results

I would like to ask for solution or advice on strange result that glmer.nb from lme4 generated when simulating using simR package. I’m working on longitudinal gut microbiome abundance data (23 ...
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25 views

Bootstrapping in logistic regression with sparse binary variable

I would like to estimate the probability of a relation between two entities. The data set includes information of many relations between many entities, and information on covariates for each entity. ...
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1answer
22 views

Using prior knowledge about correlated variable in ridge regression

I am wondering what methods are available for incorporating prior knowledge of some variable that is correlated with the unknown regression coefficients in a ridge regression. I have a sparse matrix ...
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20 views

How to control the level of sparsity on sgPLS and spls packages?

I am trying to use a (group) sparse PLS algorithm on a regression problem with an univariate response variable $y$, and I found the packages sgPLS and ...
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How to force auto encoder learn sparse data?

My data is sparse consisting of only zeros and a few ones. Since majority of values are zero, an auto encoder leans toward outputting just zeros. How can I force the network to learn the cells ...
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43 views

Why is computation of scores in Sparse PCA different from T=XP?

I am recently learning Sparse PCA. From a lately published paper All sparse PCA models are wrong, but some are useful. Part I: Computation of scores, residuals and explained variance I learned that ...
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For ridge regression, show if $K$ columns of $X$ are identical then we must have same corresponding parameters

Show if $K$ columns of $X$, $({X_{j1}, X_{j2}...X_{jk}}) $are identical then we must have $\hat\beta_{j1},\hat\beta_{j2},...\hat\beta_{jk} $ are same in the ridge regression: $$\hat\beta = \underset{...
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34 views

Compact encoding (vectorization) of unbounded sets

Question I have a set of sets. Each set is unbounded. I would like to find a methodology to encode (vectorize) each subset. I am more specifically interested in memory efficient solutions. ...
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1answer
26 views

Why atoms in the dictionary of Dictionary Learning method are not required to be orthogonal?

According to Sparse Dictionary Learning (wiki), Sparse dictionary learning is a representation learning method which aims at finding a sparse representation of the input data (also known as sparse ...
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55 views

Sparse PCA for $p >> n$ solution with Elastic Net

I was reading about the sparse principal component approach by Zou, Hastie and Tibshirani but I do not quite understand how they handle the $p \gg n$ case in their paper. To derive the sparse axis, ...
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How to conduct k-fold cross-validation with spare outcomes?

In many applications of machine learning, the outcome vector is sparse - e.g. containing millions of 0s and a handful of 1s. When the outcome vector is sparse, many of the training sets in k-fold ...
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31 views

Correaltion between sparse variables

I have an Events x People matrix M, where a cell (e,p) gives the score of person j at event e. Let E be the total number of events. Each person has attended a lot of events, say 0.3*E at an average. ...
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237 views

How is explained variance in sparse PCA calculated?

Sparse PCA is a technique proposed by Zou et all in this paper. In usual PCA the obtained loadings are orthonormal, and the resulting scores are uncorrelated. However, in sparse PCA you give up these ...
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96 views

Using Pearson correlation coefficient in sparse data

I have been using the cor function in R to compare correlation between my variables. The data did pretty poorly with 2/3 of them having a correlation close to 1 with some other variable. However the ...
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What does Sparse PCA implementation in Python do?

I am interested on using sparse PCA in python and I found the sklearn implementation. However, I think this python implementation solves a different problem than the original sparse pca algorithm ...
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26 views

How does Data Augmentation work for supervised learning models?

I've ran into a few Kaggle competitions where the winning solution used data augmentation, and a new ML platform, which claimed to help with Data Augmentation. Use cases were imbalanced classes and ...
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36 views

Computation of generalized least squares solutions of large sparse systems

Suppose $X$ and $\Omega$ are large sparse matrices, with $\Omega$ symmetric positive definite (but not diagonal), and $y$ is a vector. I want to find the generalized least squares solution: $$\hat\...
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method for determing the important factor for high dimension categorical data

I have around 1000 people with total 400 categorical features, but each one will only have subset of those 400 features(ranging from 3-60 for this population), thus the dataset is fairly sparse. Now I ...
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897 views

Shrinkage priors

I am building a Bayesian model where I to put shrinkage priors such as spike and slab, horseshoe prior, etc on some parameters for feature selection, but I am not able to decide which one is the best. ...
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261 views

What are the benefits of sparse representations and sparse parameters?

What are their benefits? I know sparse parameters are a different story than sparse representations, but I want to know how each of these can benefit us and which one is more important than the other ...
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66 views

Extracting the right summary statistics from zero-inflated data sets (i.e. a sparse matrix where everything non-zero is a statistical outlier)

I'm a consumer tech startup founder with rudimentary background in statistics. I need help in processing a large, sparse matrix. I'm logging all actions users are undertaking in my app. I then ...
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How to interpret the learning curve of a LinearRegression for sparse data?

I have a dataset of shape ca.(4800, 350). Both the dataset X as well as the response y is very sparse (ca. 3500 samples with y=0). I wanted to take a look at the learning curve to estimate the bias-...
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101 views

Sparse linear poorly constrained least-squares problem

I have a somewhat simple linear problem. I have data $D$ (a vector with a few million elements), the parameter vector $X$ (a couple of thousands elements) and the design matrix $A$ which is extremely ...
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137 views

Combining many sparse binary variables

Based on kjetil b halvorsen suggestion, I rephrased my problem: My problem is analogous to the following: i am supposed to predict if a high school student will go to university (Yes/No). I have ...
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1answer
38 views

Nonlinear approximation of a sparse linear transformation

Suppose that we have $y = Ax$ where $x$ is a vector of size $m \times 1$, $A$ is a sparse matrix with size $n \times m$. Suppose that $n \times m$ is very large and we wish to find a non-linear ...
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66 views

How to build a machine learning model from sparse features with class imbalance?

I have around 10 numerical features and 1 class/target (e.g., visitors count of a website). All of them are sparse. Sparsity is around %70-80. The median of the class/target is zero. Is there a good ...
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325 views

Clustering Binary and Continuous Features

If you need to cluster a dataset with the following characteristics: It has a mix of binary and continuous features. It is very sparse. For most features, you only have values for 15% of the ...
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27 views

Why neural network does not learn sparse relationship [duplicate]

The universal approximation theorem says that a neural network can be used to approximate any continuous function under some regular conditions with arbitrarily small approximation error, provided we ...
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25 views

Probability of sparse spectrum

Consider a vector $v$ such that $v \sim \mathrm{Unif}(\mathbb{S}^{d-1})$, the uniform distribution on the unit sphere in $d$ dimensions. Question: is there an upper bound on the probability that $v$ ...
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Is it useful to use sparse regression (e.g. Lasso) when the number of observations is significantly larger than the number of covariates?

I'm learning about penalized/sparse regression and I noticed that the examples used for penalized/sparse regression, e.g. Lasso, are usually cases where the number of observations is significantly ...
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178 views

How to conduct a principal component analysis on data set with large number of zeros

I have data for percentage cover of plant species in 500 sites. There are columns for 30 different species in the data set and I would like to drastically reduce this down to a manageable number of ...
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153 views

Does anyone know the rank of the Netflix Prize dataset?

I'm looking into the Netflix Prize at the moment. We model the dataset as an $n \times m$ matrix, where $n$ is the number of users and $m$ is the number of movies. Does anyone know the rank of the ...
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1k views

Autoencoder for sparse data

Suppose I have a big (1,000x20,000) sparse (95% of elements are zeros) matrix with counts. I want to use autoencoder to encode-decode this matrix. How should I do it? Are there any tricks or ...
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185 views

estimate precision matrix with given spatial sparsity pattern

I have a set of $n$ measurements of $p$ variables $\xi_i$. I am interested in the inverse covariance or precision matrix $P$ of the variables, but because $p \gg n$ and because of limited storage ($p$ ...
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450 views

LSTM time series forecasting on sparse dataset

I am working on the LSTM time series forecasting of solar energy production. The available data is one year on a half hourly basis. More than 60% of the data values are zero as the PV stations cannot ...
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59 views

Longitudinal study - generalised linear mixed model - dealing with very wide confidence intervals due to sparsity in the outcome

I am conducting a treatment evaluation using administrative data. It is a population-based study of all people diagnosed with a specific disorder in two calendar years (N = 2300). I have run a GLMM ...
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143 views

Literature on $\ell_q$ LASSO, $q < 1$

I am not sure how is $\ell_q$-LASSO called, but here I am talking about LASSO regression, with $\| \beta \|_{\ell_q}$ regularization, $q< 1$. In popular literature, such as Elements of Statistical ...

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