fix: remove problematic defaults from sample_last_cit() parameters

R/games.R

@@ -2149,9 +2149,13 @@ smallworld <- function(...) constructor_spec(sample_smallworld, ...)
 #' @param n Number of vertices.
 #' @param edges Number of edges per step.
 #' @param agebins Number of aging bins.
+#'   Must be at least 1.
+#'   This determines how finely the aging process is discretized.
 #' @param pref Vector (`sample_last_cit()` and `sample_cit_types()` or
 #'   matrix (`sample_cit_cit_types()`) giving the (unnormalized) citation
 #'   probabilities for the different vertex types.
+#'   For `sample_last_cit()`, this should be a numeric vector of length `agebins + 1`.
+#'   A common choice is a power-law decay, e.g., `(1:(agebins + 1))^-3`.
 #' @param directed Logical scalar, whether to generate directed networks.
 #' @param types Vector of length \sQuote{`n`}, the types of the vertices.
 #'   Types are numbered from zero.
@@ -2161,12 +2165,20 @@ smallworld <- function(...) constructor_spec(sample_smallworld, ...)
 #' @author Gabor Csardi \email{csardi.gabor@@gmail.com}
 #' @keywords graphs
 #' @family games
+#' @examples
+#' # Create a citation graph with 100 vertices, 5 age bins,
+#' # and preferential attachment following a t^-3 power-law decay
+#' g <- sample_last_cit(100, edges = 1, agebins = 5, pref = (1:6)^-3)
+#'
+#' # The preference vector determines how likely vertices in each age bin
+#' # are to receive citations. Newer vertices (lower indices) are preferred.
+#' g2 <- sample_last_cit(200, edges = 2, agebins = 10, pref = (1:11)^-2)
 #' @export
 sample_last_cit <- function(
   n,
   edges = 1,
-  agebins = n / 7100,
-  pref = (1:(agebins + 1))^-3,
+  agebins,
+  pref,
   directed = TRUE
 ) {
   on.exit(.Call(R_igraph_finalizer))

src/.gitignore

@@ -5,3 +5,4 @@
 /Makevars
 *.gcda
 *.gcno
+*.dd

tests/testthat/test-games.R

@@ -839,3 +839,47 @@ test_that("Dot product rng gives warnings", {
     paste0("Greater than 1 connection probability ", "in dot-product graph")
   )
 })
+
+test_that("sample_last_cit() works with explicit parameters", {
+  withr::local_seed(42)
+  # Basic test with small graph
+  g <- sample_last_cit(100, edges = 1, agebins = 5, pref = (1:6)^-3)
+  expect_equal(vcount(g), 100)
+  expect_equal(ecount(g), 99)
+  expect_true(is_directed(g))
+
+  # Test with more edges per step
+  g2 <- sample_last_cit(50, edges = 2, agebins = 3, pref = (1:4)^-2)
+  expect_equal(vcount(g2), 50)
+  expect_equal(ecount(g2), 98) # (50 - 1) * 2
+
+  # Test undirected version
+  g3 <- sample_last_cit(
+    30,
+    edges = 1,
+    agebins = 2,
+    pref = c(1, 0.5, 0.25),
+    directed = FALSE
+  )
+  expect_equal(vcount(g3), 30)
+  expect_false(is_directed(g3))
+})
+
+test_that("sample_last_cit() requires agebins and pref parameters", {
+  expect_error(
+    sample_last_cit(100),
+    'argument "agebins" is missing, with no default'
+  )
+
+  expect_error(
+    sample_last_cit(100, agebins = 5),
+    'argument "pref" is missing, with no default'
+  )
+})
+
+test_that("sample_last_cit() validates agebins > 0", {
+  expect_error(
+    sample_last_cit(100, edges = 1, agebins = 0, pref = c(1)),
+    "Number of age bins must be at least 1"
+  )
+})