Questions tagged [singular-matrix]

A matrix is singular when its determinant is 0; for such matrices, the inverse is not defined. Also, related topics like singular fits

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How do I resolve singularity issues related to my random effect term in LMM

I am trying to run a linear mixed model (LMM) to observe how CH4 and CO2 fluxes change over time. I have a randomized block design with repeated measures over time. I also have an unequal sample size, ...
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Does Factor Analysis completely mitigate the singular covariance matrix problem?

Background I have been trying to understand Stanford CS 229’s lecture about Factor Analysis and the accompanying lecture notes. The lecturer introduced Factor Analysis as a way to mitigate the ...
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lmer (lme4) nested random structure gives singular fit

I'm running the following model on some reaction time data: ...
68 views

Regression with single-observation dummies: F-test under heteroskedasticity

I have a linear regression model with an intercept and a few dummy variables. Each of the dummies indicate a single observation, so the fit is perfect for these observations. Having fit the model, the ...
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Solutions to a 'singular fit' in generalized linear mixed-effects models

What are common causes of a 'singular fit' in generalized linear mixed-effects models (GLMMs), especially when including random intercepts for grouping variables? When using the ...
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Linear Mixed Model equation (as of lme4 package)

I am trying to derive the equations of a linear mixed model as specified in the documentation of the lme4 package: "Fitting Linear Mixed-Effects Models using lme4" jstatsoft.org/article/view/v067i01 ...
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1 vote
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lme4 mixed model unbalanced error factors + singular fit

I am studying the effects of 5 treatments (CT,CCM,CCI,F, S) on grape yield. My experimental design consists in: 5 treatments and 2 farms (SG, MT) which I use as block. I created an additional ...
1 vote
2k views

Singular fit error caused by random factor

I'm trying to fit a generalised mixed model for some embryo data and I am getting the error for singular fit. my model is ...
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5k views

lme4 lmer() multilevel model: why do I have singular fit and a -1 correlation between random effects slope and intercept?

I'm running a varying intercepts varying slopes multilevel model with the lme4::lmer() function with no group level predictors and only one predictor: FilingFee to predict evictionfilingrate. I ...
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