From ddaebc76bce529c9b926bcc144c0cc045c4dd928 Mon Sep 17 00:00:00 2001
From: Daniel <mail@danielluedecke.de>
Date: Wed, 27 Sep 2023 15:08:20 +0200
Subject: [PATCH] Recursion in `logLik.plm()` that slows down computations:
 (#623)

Co-authored-by: Indrajeet Patil <patilindrajeet.science@gmail.com>
---
 R/logLik.R                   |  2 +-
 tests/testthat/test-logLik.R | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 tests/testthat/test-logLik.R

diff --git a/R/logLik.R b/R/logLik.R
index 90c12930b..5c42f41a5 100644
--- a/R/logLik.R
+++ b/R/logLik.R
@@ -55,7 +55,7 @@ logLik.plm <- function(object, ...) {
 
   attr(val, "nall") <- N0
   attr(val, "nobs") <- N
-  attr(val, "df") <- insight::get_df(object, type = "model")
+  attr(val, "df") <- insight::n_parameters(object) + 1L
   class(val) <- "logLik"
 
   val
diff --git a/tests/testthat/test-logLik.R b/tests/testthat/test-logLik.R
new file mode 100644
index 000000000..2691f1d3c
--- /dev/null
+++ b/tests/testthat/test-logLik.R
@@ -0,0 +1,27 @@
+test_that("logLik", {
+  skip_if_not_installed("plm")
+  skip_if_not_installed("withr")
+
+  withr::local_options(list(expressions = 25))
+  set.seed(1)
+  nnn <- 100
+  ddta <- data.frame(
+    x1 = rnorm(nnn),
+    x2 = rnorm(nnn),
+    id = rep_len(1:(nnn / 10), nnn),
+    year = rep_len(1:11, nnn)
+  )
+  ddta$y <- ddta$x1 * 0.5 - ddta$x2 * 0.5 + rnorm(nnn)
+
+  m1 <- lm(y ~ x1 + x2, data = ddta)
+  l1 <- logLik(m1)
+
+  m2 <- plm(
+    y ~ x1 + x2,
+    data = ddta,
+    model = "pooling",
+    index = c("id", "year")
+  )
+  l2 <- logLik(m2)
+  expect_equal(l1, l2, tolerance = 1e-3, ignore_attr = TRUE)
+})