case that total is 0

egusahiroaki · Dec 29, 2019 · 291c1b9 · 291c1b9
1 parent 8ec3990
commit 291c1b9
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diff --git a/index.js b/index.js
@@ -1,6 +1,12 @@
 const jStat = require("jstat");
 
 const BinomialProportion = (count, nobs, alpha = 0.05, method = "normal") => {
+  if (nobs === 0) {
+    return {
+      lowerBound: 0, value: 0, upperBound: 0
+    }
+  }
+
   const z = -1 * jStat.normal.inv(alpha / 2, 0, 1);
   let p = count / nobs;
   let sd;

diff --git a/test/test-index.js b/test/test-index.js
@@ -1,6 +1,14 @@
 import test from "ava";
 import BinomialProportion from "../index";
 
+test("total is 0", t => {
+    const result = BinomialProportion(50, 0, 0.05, "normal");
+    t.is(result.lowerBound, 0);
+    t.is(result.value, 0);
+    t.is(result.upperBound, 0);
+  });
+
+
 test("normal: Binominal(10, 500, 0.05, 'normal')", t => {
   const result = BinomialProportion(50, 500, 0.05, "normal");
   t.is(result.lowerBound, 0.07370432378270254);