residual degrees of freedom

Author: aravindhebbali

NAMESPACE

@@ -87,6 +87,7 @@ export(ols_correlations)
 export(ols_eigen_cindex)
 export(ols_fpe)
 export(ols_get_data)
+export(ols_get_df)
 export(ols_get_formula)
 export(ols_get_interaction_terms)
 export(ols_get_variables)

R/ols-model-info.R

@@ -87,3 +87,20 @@ ols_get_variables <- function(model) {
 ols_get_data <- function(model) {
   model$model
 }
+
+
+#' Degrees of freedom
+#' 
+#' Returns model/residual degrees of freedom.
+#' 
+#' @param model An object of class \code{lm}.
+#'
+#' @examples
+#' model <- lm(mpg ~ wt + cyl * hp * disp + gear * drat, data = mtcars)
+#' ols_get_df(model)
+#'
+#' @export
+#'
+ols_get_df <- function(model) {
+  model$df.residual
+}

R/utils.R

@@ -94,22 +94,6 @@ ols_get_terms <- function(model) {
   attr(model$terms, 'term.label')
 }
 
-ols_get_variables <- function(model) {
-  vars  <- names(model$model)
-  n     <- length(vars)
-  resp  <- vars[1]
-  preds <- vars[2:n]
-  list(response = resp, predictors = preds)
-}
-
-ols_get_data <- function(model) {
-  model$model
-}
-
-ols_get_df <- function(model) {
-  model$df.residual
-}
-
 ols_get_intercept <- function(model) {
   model$coefficients[[1]]
 }

man/ols_get_df.Rd

@@ -47,3 +47,10 @@ test_that("model data is returned", {
   expect_equal(want, got)
 })
 
+test_that("residual degrees of freedom is returned", {
+  model <- lm(mpg ~ wt * cyl + vs * hp * gear + carb, data = mtcars)
+  want  <- 20
+  got   <- ols_get_df(model)
+  expect_equal(want, got)
+})
+