jedifran · May 30, 2012 02:32 · May 30, 2012
diff --git a/findPrimes.R b/findPrimes.R
@@ -0,0 +1,41 @@
+##################################################################
+# Brute force method for finding all the prime numbers between
+# nMin and nMax
+##################################################################
+
+findPrimes <- function(nMin, nMax) {
+    # make sure min number is larger than 1, and break if true
+    if (nMin == 1) 
+        stop("\n\n **** Error: Please ensure nMin is larger than 1 (nMin > 1) ****")
+
+    # make sure nMax isnt too large!
+    if (nMax > 1e+08) 
+        stop("\n\n **** Error: nMax too large!!, try nMax < 1e8 ****")
+
+    # create a test range going from nMin to nMax
+    test.range = c(nMin:nMax)
+
+    # create iterator it
+    it <- 2
+
+    # iterate through test.range looking for multiples of smaller numbers
+    while (it < nMax) {
+        if (it %in% test.range) {
+            #test whether 'it' is in test.range
+            test.range <- sort(c(it, test.range[test.range%%it != 0]))  #if yes, then remove multiples amd ensure 'it' is added to updated list. this ensures small primes remain in list.
+        } else {
+            test.range <- test.range[test.range%%it != 0]  #if no, then remove large multiples
+        }
+        it <- it + 1
+    }
+    test.range
+} 
+
+
+
+#######################################
+# Usage 
+#######################################
+
+findPrimes(11,87)
+
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