feat: diversity function

src/utils/diversity.ts

@@ -0,0 +1,36 @@
+const count = (data: number[] | string[], stair = 0): {[key: string | number]:number} => {
+    let count : {[key: string | number]:number} = {};
+    data.forEach((d)=>{
+        if (stair > 0) {
+            if (typeof d === 'string'){
+                console.log("stair is not defined for string data");
+                return {};
+            }
+            else d = Math.floor(d / stair);
+        }
+        if (count[d] === undefined) count[d] = 0;
+        count[d] += 1;
+    });
+    return count;
+}
+
+// opts := 0 -> no normalization
+// otherwise -> normalize
+export const gini_simpson = (data: number[] | string[], stair = 0, opts = 0): number => {
+    const n = data.length;
+    let cnt = count(data, stair);
+    let sum = 0;
+    sum = Object.values(cnt).reduce((a,b) => a+b*(b-1));
+    sum = 1 - sum / (n*(n-1));
+    if (opts > 0) sum = sum / (1 - 1/opts);
+    return sum;
+}
+
+export const shannon = (data: number[] | string[], stair = 0): number => {
+    const n = data.length;
+    let cnt = count(data, stair);
+    let sum = 0;
+    sum = Object.values(cnt).reduce((a,b) => a+b*Math.log(b));
+    sum = -sum / n;
+    return sum;
+}