September 2017 Update

Task/Factorial/Gnuplot/factorial-2.gnuplot

@@ -0,0 +1,11 @@
+# Using int(n) allows non-integer "n" inputs with the factorial
+# calculated on int(n) in that case.
+# Arranging the condition as "n>=2" avoids infinite recursion if
+# n==NaN, since any comparison involving NaN is false.  Could change
+# "1" to an expression like "n*0+1" to propagate a NaN input to the
+# output too, if desired.
+#
+factorial(n) = (n >= 2 ? int(n)*factorial(n-1) : 1)
+set xrange [0:4.95]
+set key left
+plot factorial(x)