docs: use withr to fix the seed for a random example

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add correct seed

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R/games.R

@@ -817,24 +817,97 @@ random.graph.game <- erdos.renyi.game
 #' is_simple(vl_graph) # always TRUE
 #'
 #' ## Exponential degree distribution
-#' ## Note, that we correct the degree sequence if its sum is odd
-#' exponential_degrees <- sample(1:100, 100, replace = TRUE, prob = exp(-0.5 * (1:100)))
+#' ## We fix the seed as there's no guarantee
+#' ##  that randomly picked integers will form a graphical degree sequence
+#' ## (i.e. that there's a graph with these degrees)
+#' ## withr::with_seed(42, {
+#' ## exponential_degrees <- sample(1:100, 100, replace = TRUE, prob = exp(-0.5 * (1:100)))
+#' ## })
+#' exponential_degrees <- c(
+#'   5L, 6L, 1L, 4L, 3L, 2L, 3L, 1L, 3L, 3L, 2L, 3L, 6L, 1L, 2L,
+#'   6L, 8L, 1L, 2L, 2L, 5L, 1L, 10L, 6L, 1L, 2L, 1L, 5L, 2L, 4L,
+#'   3L, 4L, 1L, 3L, 1L, 4L, 1L, 1L, 5L, 2L, 1L, 2L, 1L, 8L, 2L, 7L,
+#'   5L, 3L, 8L, 2L, 1L, 1L, 2L, 4L, 1L, 3L, 3L, 1L, 1L, 2L, 3L, 9L,
+#'   3L, 2L, 4L, 1L, 1L, 4L, 3L, 1L, 1L, 1L, 1L, 2L, 1L, 3L, 1L, 1L,
+#'   2L, 1L, 2L, 1L, 1L, 3L, 3L, 2L, 1L, 1L, 1L, 1L, 3L, 1L, 1L, 6L,
+#'   6L, 3L, 1L, 2L, 3L, 2L
+#' )
+#' ## Note, that we'd have to correct the degree sequence if its sum is odd
 #' is_exponential_degrees_sum_odd <- (sum(exponential_degrees) %% 2 != 0)
 #' if (is_exponential_degrees_sum_odd) {
 #'   exponential_degrees[1] <- exponential_degrees[1] + 1
 #' }
 #' exp_vl_graph <- sample_degseq(exponential_degrees, method = "vl")
 #' all(degree(exp_vl_graph) == exponential_degrees)
 #'
+#' ## An example that does not work
+#' @examplesIf rlang::is_interactive()
+#' ## withr::with_seed(11, {
+#' ## exponential_degrees <- sample(1:100, 100, replace = TRUE, prob = exp(-0.5 * (1:100)))
+#' ## })
+#' exponential_degrees <- c(
+#'   1L, 1L, 2L, 1L, 1L, 7L, 1L, 1L, 5L, 1L, 1L, 2L, 5L, 4L, 3L,
+#'   2L, 2L, 1L, 1L, 2L, 1L, 3L, 1L, 1L, 1L, 2L, 2L, 1L, 1L, 2L, 2L,
+#'   1L, 2L, 1L, 4L, 3L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 3L, 1L, 4L, 3L,
+#'   1L, 2L, 4L, 2L, 2L, 2L, 1L, 1L, 2L, 2L, 4L, 1L, 2L, 1L, 3L, 1L,
+#'   2L, 3L, 1L, 1L, 2L, 1L, 2L, 3L, 2L, 2L, 1L, 6L, 2L, 1L, 1L, 1L,
+#'   1L, 1L, 2L, 2L, 1L, 4L, 2L, 1L, 3L, 4L, 1L, 1L, 3L, 1L, 2L, 4L,
+#'   1L, 3L, 1L, 2L, 1L
+#' )
+#' ## Note, that we'd have to correct the degree sequence if its sum is odd
+#' is_exponential_degrees_sum_odd <- (sum(exponential_degrees) %% 2 != 0)
+#' if (is_exponential_degrees_sum_odd) {
+#'   exponential_degrees[1] <- exponential_degrees[1] + 1
+#' }
+#' exp_vl_graph <- sample_degseq(exponential_degrees, method = "vl")
+#'
+#' @examples
 #' ## Power-law degree distribution
+#' ## We fix the seed as there's no guarantee
+#' ##  that randomly picked integers will form a graphical degree sequence
+#' ## (i.e. that there's a graph with these degrees)
+#' ## withr::with_seed(1, {
+#' ##  powerlaw_degrees <- sample(1:100, 100, replace = TRUE, prob = (1:100)^-2)
+#' ## })
+#' powerlaw_degrees <- c(
+#'   1L, 1L, 1L, 6L, 1L, 6L, 10L, 2L, 2L, 1L, 1L, 1L, 2L, 1L, 3L,
+#'   1L, 2L, 43L, 1L, 3L, 9L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 4L, 1L,
+#'   1L, 1L, 1L, 1L, 3L, 2L, 3L, 1L, 2L, 1L, 3L, 2L, 3L, 1L, 1L, 3L,
+#'   1L, 1L, 2L, 2L, 1L, 4L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 7L, 1L,
+#'   1L, 1L, 2L, 1L, 1L, 3L, 1L, 5L, 1L, 4L, 1L, 1L, 1L, 5L, 4L, 1L,
+#'   3L, 13L, 1L, 2L, 1L, 1L, 2L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 2L,
+#'   5L, 3L, 3L, 1L, 1L, 3L, 1L
+#' )
 #' ## Note, that we correct the degree sequence if its sum is odd
-#' powerlaw_degrees <- sample(1:100, 100, replace = TRUE, prob = (1:100)^-2)
 #' is_exponential_degrees_sum_odd <- (sum(powerlaw_degrees) %% 2 != 0)
 #' if (is_exponential_degrees_sum_odd) {
 #'   powerlaw_degrees[1] <- powerlaw_degrees[1] + 1
 #' }
 #' powerlaw_vl_graph <- sample_degseq(powerlaw_degrees, method = "vl")
 #' all(degree(powerlaw_vl_graph) == powerlaw_degrees)
+#'
+#' ## An example that does not work
+#' @examplesIf rlang::is_interactive()
+#' ## withr::with_seed(2, {
+#' ##  powerlaw_degrees <- sample(1:100, 100, replace = TRUE, prob = (1:100)^-2)
+#' ## })
+#' powerlaw_degrees <- c(
+#'   1L, 2L, 1L, 1L, 10L, 10L, 1L, 4L, 1L, 1L, 1L, 1L, 2L, 1L, 1L,
+#'   4L, 21L, 1L, 1L, 1L, 2L, 1L, 4L, 1L, 1L, 1L, 1L, 1L, 14L, 1L,
+#'   1L, 1L, 3L, 4L, 1L, 2L, 4L, 1L, 2L, 1L, 25L, 1L, 1L, 1L, 10L,
+#'   3L, 19L, 1L, 1L, 3L, 1L, 1L, 2L, 8L, 1L, 3L, 3L, 36L, 2L, 2L,
+#'   3L, 5L, 2L, 1L, 4L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L,
+#'   1L, 4L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 4L, 18L, 1L, 2L, 1L, 21L,
+#'   1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L
+#' )
+#' ## Note, that we correct the degree sequence if its sum is odd
+#' is_exponential_degrees_sum_odd <- (sum(powerlaw_degrees) %% 2 != 0)
+#' if (is_exponential_degrees_sum_odd) {
+#'   powerlaw_degrees[1] <- powerlaw_degrees[1] + 1
+#' }
+#' powerlaw_vl_graph <- sample_degseq(powerlaw_degrees, method = "vl")
+#' all(degree(powerlaw_vl_graph) == powerlaw_degrees)
+#'
 sample_degseq <- function(out.deg, in.deg = NULL,
                           method = c("simple", "vl", "simple.no.multiple", "simple.no.multiple.uniform")) {
   method <- igraph.match.arg(method)