# Questions tagged [singular]

A matrix is singular when its determinant is 0; for such matrices, the inverse is not defined.

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### Linear dependency among columns and rows

Singular matrix is defined as square matrix with the determinant of zero. The determinant of zero occurs when matrix columns are linearly dependent (i.e. one of the columns can be defined as a linear ...
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### “System is computationally singular” error in igraph

I'm using igraph to build some indicators about the railway network. I have a graph with 9,000 nodes. I want to calculate the distance resistance using ...
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### Singular Matrix and Linear Dependency

Singular matrix is defined as a square matrix with determinant of zero. I am aware that linear dependency among columns or rows leads to determinant being equal to zero (e.g. one column is a linear ...
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### Problematic data for regression model

This is a follow-up question to Which model for my data? (testing the differences in slope for three groups). The solution from there works (big thanks to Heteroskedastic Jim!), but I have a problem ...
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### Multinomial logistic regression on categorical data results in singular matrix

I have a categorical dataset from a biological sampling study consisting of six variables, see http://pastebin.com/ncLzw0Mt for the actual dataset. ...
Suppose I have 2 vectors of random variables $\boldsymbol\theta_1 \in \mathbb{R^n}$ and $\boldsymbol\theta_2 \in \mathbb{R^m}$ with asymptotic covariance $\Sigma_1$ and $\Sigma_2$ respectively. I want ...
I want to do a linear regression $Y = X\beta + e$, but some of the observations (rows in $X$) are identical (about 30 000 out of 50 000 remain after deleting all duplicates), so when I try to ...