add some utility functions

R/utilities.R

@@ -0,0 +1,29 @@
+# Check if the number of objectives is the same for given (sets of) points.
+#
+# We frequently need to check whether the dimension of an approximation set is
+# equal to the dimension of the ideal point and/or nadir point. This does exactly
+# that assertion for an arbitrary number of arguments.
+#
+# @param ... [any]
+#   Vectors or matrizes.
+# @return Nothing. Stops if not all dimensions are equal.
+assertSameDimensions = function(...) {
+  xs = list(...)
+  dims = sapply(xs, function(x) {
+    # we store vectors one per column
+    return(if (is.matrix(x)) nrow(x) else length(x))
+  })
+  if (!hasAllEqualElements(dims)) {
+    stopf("All point sets and points need to be of the same dimension.")
+  }
+}
+
+# Check whether all elements of an vector are equal.
+#
+# @param x [vector]
+#   Input vector.
+# @return [logical(1)]
+hasAllEqualElements = function(x) {
+  return(length(unique(x)) == 1)
+}
+