set-operations concept

concepts/set-operations/.meta/config.json

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+{
+  "authors": ["colinleach"],
+  "contributors": [],
+  "blurb": "Core R provides several functions that perform set-like operations on vectors."
+}

concepts/set-operations/about.md

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+# Introduction
+
+R has no separate Set datatype, instead using a variety of functions to perform similar operations on vectors.
+
+We have already seen `%in%` to test for set membership:
+
+```R
+2 %in% 1:10 # TRUE
+12 %in% 1:10 # FALSE
+```
+
+Relevant functions include `unique` to remove duplicates, plus `union()`, `intersect()` and `setdiff()` to operate on pairs of sets.
+
+```R
+> set_1 <- c("a", "b", "c", "b", "a")
+> unique(set_1) # deduplicate
+[1] "a" "b" "c"
+
+> set_2 <- c('a', "c", "d")
+> union(set_1, set_2) # values in either set
+[1] "a" "b" "c" "d"
+
+> intersect(set_1, set_2) # values in both sets
+[1] "a" "c"
+
+> setdiff(set_1, set_2) # values in set_1 but not set_2
+[1] "b"
+
+> setdiff(set_2, set_1)
+[1] "d"
+```
+
+## The `hashtable` package
+
+The vector operations described above are part of core R.
+These are useful for small problems but become slow for large sets.
+
+The `hashtable` package provides implementations of `hashmap` and `hashset` which scale better.
+Like most external packages, this is not available within Exercism, but is worth investigating for real-world problems.

concepts/set-operations/introduction.md

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+# Introduction
+
+R has no separate Set datatype, instead using a variety of functions to perform similar operations on vectors.
+
+We have already seen `%in%` to test for set membership:
+
+```R
+2 %in% 1:10 # TRUE
+12 %in% 1:10 # FALSE
+```
+
+Relevant functions include `unique` (to remove duplicates), `union()`, `intersect()` and `setdiff()` to operate on pairs of sets.
+Details are available online.

concepts/set-operations/links.json

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+[
+  {
+    "url": "https://search.r-project.org/CRAN/refmans/generics/html/setops.html",
+    "description": "Set Operations"
+  }
+]

config.json

@@ -582,6 +582,11 @@
       "slug": "basics",
       "name": "Basics"
     },
+    {
+      "uuid": "85db3d8c-dfec-424c-9682-caa8611db8f8",
+      "slug": "set-operations",
+      "name": "Set Operations"
+    },
     {
       "uuid": "2751b6f2-7d71-4397-b063-9bf927a57756",
       "slug": "booleans",