Data commit

Task/Almost-prime/R/almost-prime.r

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+#===============================================================
+# Find k-Almost-primes
+# R implementation
+#===============================================================
+#---------------------------------------------------------------
+# Function for prime factorization from Rosetta Code
+#---------------------------------------------------------------
+
+findfactors <- function(n) {
+  d <- c()
+  div <- 2; nxt <- 3; rest <- n
+  while( rest != 1 ) {
+    while( rest%%div == 0 ) {
+      d <- c(d, div)
+      rest <- floor(rest / div)
+    }
+    div <- nxt
+    nxt <- nxt + 2
+  }
+  d
+}
+
+#---------------------------------------------------------------
+# Find k-Almost-primes
+#---------------------------------------------------------------
+
+almost_primes <- function(n = 10, k = 5) {
+
+  # Set up matrix for storing of the results
+
+  res <- matrix(NA, nrow = k, ncol = n)
+  rownames(res) <- paste("k = ", 1:k, sep = "")
+  colnames(res) <- rep("", n)
+
+  # Loop over k
+
+  for (i in 1:k) {
+
+    tmp <- 1
+
+    while (any(is.na(res[i, ]))) { # Keep looping if there are still missing entries in the result-matrix
+      if (length(findfactors(tmp)) == i) { # Check number of factors
+        res[i, which.max(is.na(res[i, ]))] <- tmp
+      }
+      tmp <- tmp + 1
+    }
+  }
+  print(res)
+}