June 2018 Update

Task/Benfords-law/Factor/benfords-law.factor

@@ -0,0 +1,29 @@
+USING: assocs compiler.tree.propagation.call-effect formatting
+kernel math math.functions math.statistics math.text.utils
+sequences ;
+IN: rosetta-code.benfords-law
+
+: expected ( n -- x ) recip 1 + log10 ;
+
+: next-fib ( vec -- vec' )
+    [ last2 ] keep [ + ] dip [ push ] keep ;
+
+: data ( -- seq ) V{ 1 1 } clone 998 [ next-fib ] times ;
+
+: 1st-digit ( n -- m ) 1 digit-groups last ;
+
+: leading ( -- seq ) data [ 1st-digit ] map ;
+
+: .header ( -- )
+    "Digit" "Expected" "Actual" "%-10s%-10s%-10s\n" printf ;
+
+: digit-report ( digit digit-count -- digit expected actual )
+    dupd [ expected ] dip 1000 /f ;
+
+: .digit-report ( digit digit-count -- )
+    digit-report "%-10d%-10.4f%-10.4f\n" printf ;
+
+: main ( -- )
+    .header leading histogram [ .digit-report ] assoc-each ;
+
+MAIN: main