Data commit

Task/Cumulative-standard-deviation/Kotlin/cumulative-standard-deviation.kotlin

@@ -0,0 +1,20 @@
+// version 1.0.5-2
+
+class CumStdDev {
+    private var n = 0
+    private var sum = 0.0
+    private var sum2 = 0.0
+
+    fun sd(x: Double): Double {
+        n++
+        sum += x
+        sum2 += x * x
+        return Math.sqrt(sum2 / n - sum * sum / n / n)
+    }
+}
+
+fun main(args: Array<String>) {
+    val testData = doubleArrayOf(2.0, 4.0, 4.0, 4.0, 5.0, 5.0, 7.0, 9.0)
+    val csd = CumStdDev()
+    for (d in testData) println("Add $d => ${csd.sd(d)}")
+}