ESM: Ported MS and Entropy operations

src/core/operations/ChiSquare.mjs

@@ -0,0 +1,53 @@
+/**
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2017
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+
+/**
+ * Chi Square operation
+ */
+class ChiSquare extends Operation {
+
+    /**
+     * ChiSquare constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Chi Square";
+        this.module = "Default";
+        this.description = "Calculates the Chi Square distribution of values.";
+        this.inputType = "ArrayBuffer";
+        this.outputType = "number";
+        this.args = [];
+    }
+
+    /**
+     * @param {ArrayBuffer} input
+     * @param {Object[]} args
+     * @returns {number}
+     */
+    run(input, args) {
+        const data = new Uint8Array(input);
+        const distArray = new Array(256).fill(0);
+        let total = 0;
+
+        for (let i = 0; i < data.length; i++) {
+            distArray[data[i]]++;
+        }
+
+        for (let i = 0; i < distArray.length; i++) {
+            if (distArray[i] > 0) {
+                total += Math.pow(distArray[i] - data.length / 256, 2) / (data.length / 256);
+            }
+        }
+
+        return total;
+    }
+
+}
+
+export default ChiSquare;