[WIP] API doc for methods applied to model object

[ajinkya-k]

#607 pointed out that the API doc is missing for quite a few methods. This PR adds them.

Also removes lm and glm from the list of methods applied to fit objects in docs/index.md

Tracker

• adjr2: adjusted R² for a linear model (an alias for adjr²)
• aic: Akaike's Information Criterion
• aicc: corrected Akaike's Information Criterion for small sample sizes
• bic: Bayesian Information Criterion
• coef: estimates of the coefficients in the model
• confint: confidence intervals for coefficients
• coeftable
• cooksdistance: Cook's distance for each observation
• deviance: measure of the model fit, weighted residual sum of squares for lm's
• dispersion: dispersion (or scale) parameter for a model's distribution
• dof: number of degrees of freedom consumed in the model
• dof_residual: degrees of freedom for residuals, when meaningful
• fitted: fitted values of the model
• loglikelihood: log-likelihood of the model
• modelmatrix: design matrix
• nobs: number of rows, or sum of the weights when prior weights are specified
• nulldeviance: deviance of the model with all predictors removed
• nullloglikelihood: log-likelihood of the model with all predictors removed
• predict: predicted values of the dependent variable from the fitted model
• r2: R² of a linear model (an alias for r²)
• residuals: vector of residuals from the fitted model
• response: model response (a.k.a the dependent variable)
• stderror: standard errors of the coefficients
• vcov: variance-covariance matrix of the coefficient estimates

fixes #607

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.82%. Comparing base (8f58b34) to head (94b73e3).

Additional details and impacted files

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  Coverage   94.82%   94.82%           
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  Files           8        8           
  Lines        1044     1044           
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  Hits          990      990           
  Misses         54       54           

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