add nodelistToEdgelist

jakobbossek · Jan 3, 2018 · 8ecf9f4 · 8ecf9f4
1 parent 707be81
commit 8ecf9f4
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diff --git a/NAMESPACE b/NAMESPACE
@@ -22,6 +22,7 @@ export(mcMSTPrim)
 export(mutEdgeExchange)
 export(mutSubgraphMST)
 export(mutUniformPruefer)
+export(nodelistToEdgelist)
 export(permutationToCharVec)
 export(permutationToEdgelist)
 export(plotEdgeFrequency)

diff --git a/R/transformations.R b/R/transformations.R
@@ -98,6 +98,28 @@ edgeListToCharVec = function(edgelist, n = NULL) {
   return(cv)
 }
 
+#' Convert sequence of nodes to edge list.
+#'
+#' @param nodelist [\code{integer}]\cr
+#'   Sequence of nodes.
+#' @template ret_edgelist
+#' @examples
+#' # first generate a random permutation, e.g., representing
+#' # a roundtrip tour in a graph
+#' nodelist = sample(1:8)
+#' # now convert into an edge list
+#' nodelistToEdgelist(nodelist)
+#' @family transformation functions
+#' @export
+nodelistToEdgelist = function(nodelist) {
+  n = length(nodelist)
+  edgelist = matrix(NA, nrow = 2L, ncol = n - 1L)
+  for (i in 1:(n - 1L)) {
+    edgelist[, i] = nodelist[i:(i + 1L)]
+  }
+  return(edgelist)
+}
+
 #' Convert characteristic vector to edge list.
 #'
 #' @template arg_charvec

diff --git a/man/charVecToEdgelist.Rd b/man/charVecToEdgelist.Rd
diff --git a/man/edgeListToCharVec.Rd b/man/edgeListToCharVec.Rd
diff --git a/man/nodelistToEdgelist.Rd b/man/nodelistToEdgelist.Rd
diff --git a/man/permutationToCharVec.Rd b/man/permutationToCharVec.Rd
diff --git a/man/permutationToEdgelist.Rd b/man/permutationToEdgelist.Rd
diff --git a/man/prueferToCharVec.Rd b/man/prueferToCharVec.Rd
diff --git a/man/prueferToEdgeList.Rd b/man/prueferToEdgeList.Rd
diff --git a/tests/testthat/test_transformations.R b/tests/testthat/test_transformations.R
@@ -56,3 +56,13 @@ test_that("trafo for roundtrip tours work well", {
     expect_true(all(cvec1 %in% c(0, 1)))
   }
 })
+
+test_that("trafo between node list and edge list works", {
+  for (i in 1:10L) {
+    n = sample(2:10, 1L)
+    nodelist = sample(1:10, size = n, replace = FALSE)
+    edgelist = nodelistToEdgelist(nodelist)
+    expect_matrix(edgelist, nrows = 2L, ncols = n - 1L, mode = "numeric")
+    expect_true(all(as.integer(edgelist) %in% nodelist))
+  }
+})