Show article id only on score > 0.

cmd/ir-tfidf/main.go

@@ -47,6 +47,9 @@ func main() {
 				score += float64(tf[w][article.Id]) * math.Log2(float64(len(articles) / df[w]))
 			}
 		}
+
+		if score > 0 {
 			fmt.Printf("Article %v: %v\n", article.Id, score)
 		}
 	}
+}