# Statsmodels

> Librería de modelado estadístico para Python: OLS, GLM, modelos mixtos, ARIMA, con diagnósticos, residuos e inferencia detallada. Ideal para econometría e inferencia rigurosa con tablas de coeficientes.

Fuente: https://skillsagentes.com/skills/k-dense-ai/scientific-agent-skills/statsmodels
Markdown: https://skillsagentes.com/skills/k-dense-ai/scientific-agent-skills/statsmodels.md

Repositorio: https://github.com/K-Dense-AI/scientific-agent-skills
Autor: K-Dense-AI
Licencia: BSD-3-Clause license
Actualizado: el mes pasado
Coste de contexto: 82 tok instalada, 2.5k tok al activarse, 27.1k tok con todos los archivos del bundle
Bundle: 9 archivos, 106 KB
Permisos que pide: read write edit bash

## Instalación

Un skill son archivos markdown: los mismos archivos valen para cualquier agente y lo único que cambia es el directorio de destino, es decir la bandera `--agent`. Añade `-g` para instalarlo en todos los proyectos de la máquina.

```bash
# Claude Code
npx -y skills add K-Dense-AI/scientific-agent-skills --skill statsmodels --agent claude-code
# Cursor
npx -y skills add K-Dense-AI/scientific-agent-skills --skill statsmodels --agent cursor
# Codex
npx -y skills add K-Dense-AI/scientific-agent-skills --skill statsmodels --agent codex
# Gemini CLI
npx -y skills add K-Dense-AI/scientific-agent-skills --skill statsmodels --agent gemini
# Windsurf
npx -y skills add K-Dense-AI/scientific-agent-skills --skill statsmodels --agent windsurf
# Cline
npx -y skills add K-Dense-AI/scientific-agent-skills --skill statsmodels --agent cline
```

## Qué hace

- Ajusta modelos de regresión (OLS, WLS, GLS, regresión cuantílica) y modelos lineales generalizados (logística, Poisson, Gamma)
- Analiza series temporales con ARIMA, SARIMAX, VAR y genera pronósticos
- Ejecuta diagnósticos de residuos, heterocedasticidad, autocorrelación y detecta observaciones influyentes
- Compara modelos con AIC/BIC y pruebas de razón de verosimilitud, y estima efectos causales
- Produce tablas estadísticas listas para publicación con errores estándar e intervalos de confianza

## Cuándo usarla

- Ajustar modelos de regresión o GLM con inferencia detallada (coeficientes, errores estándar, IC)
- Analizar series temporales (ARIMA, SARIMAX, VAR) o probar estacionariedad
- Necesitas econometría rigurosa en vez de solo predicción
- Comparar modelos, testear supuestos o detectar observaciones influyentes

## Cuándo no

- El objetivo es predicción pura sin necesidad de interpretar los coeficientes (usa scikit-learn)
- Necesitas selección guiada de pruebas estadísticas con reporte estilo APA (usa la skill statistical-analysis)

## Qué la activa

- "Ajusta un modelo de regresión logística con statsmodels y dame los odds ratios"
- "Corre un ARIMA sobre esta serie temporal y revisa los residuos"
- "Compara estos modelos con AIC y BIC"
- "Necesito una tabla de regresión OLS con errores estándar robustos"

## Antes de instalar

- Requiere Python 3.9+ y `uv pip install statsmodels==0.14.6`; los ejemplos de métricas predictivas también necesitan scikit-learn.
- Necesita en el PATH: rg

## Archivos

- SKILL.md — 10 KB
- references/discrete_choice.md — 17 KB
- references/glm.md — 16 KB
- references/linear_models.md — 13 KB
- references/model_selection.md — 2 KB
- references/modeling_capabilities.md — 6 KB
- references/quick_start_guide.md — 4 KB
- references/stats_diagnostics.md — 20 KB
- references/time_series.md — 19 KB

## SKILL.md

Reproducido tal cual desde K-Dense-AI/scientific-agent-skills bajo BSD-3-Clause license. Esta sección es el documento original y está en inglés.

# Statsmodels: Statistical Modeling and Econometrics

## Overview

Statsmodels is Python's premier library for statistical modeling, providing tools for estimation, inference, and diagnostics across a wide range of statistical methods. Apply this skill for rigorous statistical analysis, from simple linear regression to complex time series models and econometric analyses.

## Current Compatibility

Examples target statsmodels 0.14.6, released Dec 5, 2025. For reproducible environments, pin the primary package:

```bash
uv pip install statsmodels==0.14.6
```

Use `statsmodels.api` and `statsmodels.formula.api` for stable high-level imports, and direct module imports when examples require newer or specialized classes such as `HurdleCountModel`.

## When to Use This Skill

This skill should be used when:
- Fitting regression models (OLS, WLS, GLS, quantile regression)
- Performing generalized linear modeling (logistic, Poisson, Gamma, etc.)
- Analyzing discrete outcomes (binary, multinomial, count, ordinal)
- Conducting time series analysis (ARIMA, SARIMAX, VAR, forecasting)
- Running statistical tests and diagnostics
- Testing model assumptions (heteroskedasticity, autocorrelation, normality)
- Detecting outliers and influential observations
- Comparing models (AIC/BIC, likelihood ratio tests)
- Estimating causal effects
- Producing publication-ready statistical tables and inference

## Quick Start, Capabilities, and Model Selection

- [references/quick_start_guide.md](references/quick_start_guide.md): minimal worked
  examples for OLS, logistic regression, ARIMA, and GLM, and how to read the summary.
- [references/modeling_capabilities.md](references/modeling_capabilities.md): linear
  models, GLMs, discrete choice, time series, and the statistical tests and diagnostics.
- [references/model_selection.md](references/model_selection.md): the R-style formula API
  and model comparison.
- Per-topic detail: [references/linear_models.md](references/linear_models.md),
  [references/glm.md](references/glm.md),
  [references/discrete_choice.md](references/discrete_choice.md),
  [references/time_series.md](references/time_series.md), and
  [references/stats_diagnostics.md](references/stats_diagnostics.md).

statsmodels is for *inference* — standard errors, confidence intervals, and hypothesis
tests. Reach for scikit-learn when prediction is the goal and the coefficients do not
need interpreting.

## Best Practices

### Data Preparation

1. **Always add constant**: Use `sm.add_constant()` unless excluding intercept
2. **Check for missing values**: Handle or impute before fitting
3. **Scale if needed**: Improves convergence, interpretation (but not required for tree models)
4. **Encode categoricals**: Use formula API or manual dummy coding

### Model Building

1. **Start simple**: Begin with basic model, add complexity as needed
2. **Check assumptions**: Test residuals, heteroskedasticity, autocorrelation
3. **Use appropriate model**: Match model to outcome type (binary→Logit, count→Poisson)
4. **Consider alternatives**: If assumptions violated, use robust methods or different model

### Inference

1. **Report effect sizes**: Not just p-values
2. **Use robust SEs**: When heteroskedasticity or clustering present
3. **Multiple comparisons**: Correct when testing many hypotheses
4. **Confidence intervals**: Always report alongside point estimates

### Model Evaluation

1. **Check residuals**: Plot residuals vs fitted, Q-Q plot
2. **Influence diagnostics**: Identify and investigate influential observations
3. **Out-of-sample validation**: Test on holdout set or cross-validate
4. **Compare models**: Use AIC/BIC for non-nested, LR test for nested

### Reporting

1. **Comprehensive summary**: Use `.summary()` for detailed output
2. **Document decisions**: Note transformations, excluded observations
3. **Interpret carefully**: Account for link functions (e.g., exp(β) for log link)
4. **Visualize**: Plot predictions, confidence intervals, diagnostics

## Common Workflows

### Workflow 1: Linear Regression Analysis

1. Explore data (plots, descriptives)
2. Fit initial OLS model
3. Check residual diagnostics
4. Test for heteroskedasticity, autocorrelation
5. Check for multicollinearity (VIF)
6. Identify influential observations
7. Refit with robust SEs if needed
8. Interpret coefficients and inference
9. Validate on holdout or via CV

### Workflow 2: Binary Classification

1. Fit logistic regression (Logit)
2. Check for convergence issues
3. Interpret odds ratios
4. Calculate marginal effects
5. Evaluate classification performance (AUC, confusion matrix)
6. Check for influential observations
7. Compare with alternative models (Probit)
8. Validate predictions on test set

### Workflow 3: Count Data Analysis

1. Fit Poisson regression
2. Check for overdispersion
3. If overdispersed, fit Negative Binomial
4. Check for excess zeros (consider ZIP/ZINB)
5. Interpret rate ratios
6. Assess goodness of fit
7. Compare models via AIC
8. Validate predictions

### Workflow 4: Time Series Forecasting

1. Plot series, check for trend/seasonality
2. Test for stationarity (ADF, KPSS)
3. Difference if non-stationary
4. Identify p, q from ACF/PACF
5. Fit ARIMA or SARIMAX
6. Check residual diagnostics (Ljung-Box)
7. Generate forecasts with confidence intervals
8. Evaluate forecast accuracy on test set

## Reference Documentation

This skill includes comprehensive reference files for detailed guidance:

### references/linear_models.md
Detailed coverage of linear regression models including:
- OLS, WLS, GLS, GLSAR, Quantile Regression
- Mixed effects models
- Recursive and rolling regression
- Comprehensive diagnostics (heteroskedasticity, autocorrelation, multicollinearity)
- Influence statistics and outlier detection
- Robust standard errors (HC, HAC, cluster)
- Hypothesis testing and model comparison

### references/glm.md
Complete guide to generalized linear models:
- All distribution families (Binomial, Poisson, Gamma, etc.)
- Link functions and when to use each
- Model fitting and interpretation
- Pseudo R-squared and goodness of fit
- Diagnostics and residual analysis
- Applications (logistic, Poisson, Gamma regression)

### references/discrete_choice.md
Comprehensive guide to discrete outcome models:
- Binary models (Logit, Probit)
- Multinomial models (MNLogit, Conditional Logit)
- Count models (Poisson, Negative Binomial, Zero-Inflated, Hurdle)
- Ordinal models
- Marginal effects and interpretation
- Model diagnostics and comparison

### references/time_series.md
In-depth time series analysis guidance:
- Univariate models (AR, ARIMA, SARIMAX, Exponential Smoothing)
- Multivariate models (VAR, VARMAX, Dynamic Factor)
- State space models
- Stationarity testing and diagnostics
- Forecasting methods and evaluation
- Granger causality, IRF, FEVD

### references/stats_diagnostics.md
Comprehensive statistical testing and diagnostics:
- Residual diagnostics (autocorrelation, heteroskedasticity, normality)
- Influence and outlier detection
- Hypothesis tests (parametric and non-parametric)
- ANOVA and post-hoc tests
- Multiple comparisons correction
- Robust covariance matrices
- Power analysis and effect sizes

**When to reference:**
- Need detailed parameter explanations
- Choosing between similar models
- Troubleshooting convergence or diagnostic issues
- Understanding specific test statistics
- Looking for code examples for advanced features

**Search patterns:**
```bash
# Find information about specific models
rg "Quantile Regression" references/

# Find diagnostic tests
rg "Breusch-Pagan" references/stats_diagnostics.md

# Find time series guidance
rg "SARIMAX" references/time_series.md
```

## Common Pitfalls to Avoid

1. **Forgetting constant term**: Always use `sm.add_constant()` unless no intercept desired
2. **Ignoring assumptions**: Check residuals, heteroskedasticity, autocorrelation
3. **Wrong model for outcome type**: Binary→Logit/Probit, Count→Poisson/NB, not OLS
4. **Not checking convergence**: Look for optimization warnings
5. **Misinterpreting coefficients**: Remember link functions (log, logit, etc.)
6. **Using Poisson with overdispersion**: Check dispersion, use Negative Binomial if needed
7. **Not using robust SEs**: When heteroskedasticity or clustering present
8. **Overfitting**: Too many parameters relative to sample size
9. **Data leakage**: Fitting on test data or using future information
10. **Not validating predictions**: Always check out-of-sample performance
11. **Comparing non-nested models**: Use AIC/BIC, not LR test
12. **Ignoring influential observations**: Check Cook's distance and leverage
13. **Multiple testing**: Correct p-values when testing many hypotheses
14. **Not differencing time series**: Fit ARIMA on non-stationary data
15. **Confusing prediction vs confidence intervals**: Prediction intervals are wider

## Getting Help

For detailed documentation and examples:
- Official docs: https://www.statsmodels.org/stable/
- User guide: https://www.statsmodels.org/stable/user-guide.html
- Examples: https://www.statsmodels.org/stable/examples/index.html
- API reference: https://www.statsmodels.org/stable/api.html

## Dónde encaja

- Categoría: [Datos y analítica](https://skillsagentes.com/categorias/datos-analitica.md) — Consulta, limpia y visualiza datos sin salir del agente.
- Creador: [K-Dense-AI](https://skillsagentes.com/creators/k-dense-ai.md) — 163 skills en el directorio
- [Todas las skills](https://skillsagentes.com/skills.md)
- [Ranking de instalaciones](https://skillsagentes.com/ranking.md)

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- [Infographics](https://skillsagentes.com/skills/k-dense-ai/scientific-agent-skills/infographics.md): Crea infografías profesionales con Nano Banana Pro AI y refinamiento iterativo inteligente. Usa Gemini 3.6 Flash para revisar la calidad e integra investigación con Perplexity Sonar. Soporta 10 tipos, 8 estilos y paletas para daltonismo.
- [Latex Posters](https://skillsagentes.com/skills/k-dense-ai/scientific-agent-skills/latex-posters.md): Crea pósteres de investigación profesionales en LaTeX con beamerposter, tikzposter o baposter, para conferencias y comunicación científica: layout, colores, columnas múltiples e integración de figuras.

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