improve: improved rating algorithm wip

anuraghazra · Jul 14, 2020 · 2658a87 · 2658a87
1 parent cbd0e58
commit 2658a87
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Showing 2 changed files with 61 additions and 20 deletions.
diff --git a/src/calculateRank.js b/src/calculateRank.js
@@ -1,3 +1,21 @@
+// https://stackoverflow.com/a/5263759/10629172
+function normalcdf(mean, sigma, to) {
+  var z = (to - mean) / Math.sqrt(2 * sigma * sigma);
+  var t = 1 / (1 + 0.3275911 * Math.abs(z));
+  var a1 = 0.254829592;
+  var a2 = -0.284496736;
+  var a3 = 1.421413741;
+  var a4 = -1.453152027;
+  var a5 = 1.061405429;
+  var erf =
+    1 - ((((a5 * t + a4) * t + a3) * t + a2) * t + a1) * t * Math.exp(-z * z);
+  var sign = 1;
+  if (z < 0) {
+    sign = -1;
+  }
+  return (1 / 2) * (1 + sign * erf);
+}
+
 function calculateRank({
   totalRepos,
   totalCommits,
@@ -13,12 +31,24 @@ function calculateRank({
   const STARS_OFFSET = 0.75;
   const PRS_OFFSET = 0.5;
   const FOLLOWERS_OFFSET = 0.45;
+  const REPO_OFFSET = 1;
+
+  const ALL_OFFSETS =
+    CONTRIBS_OFFSET +
+    ISSUES_OFFSET +
+    STARS_OFFSET +
+    PRS_OFFSET +
+    FOLLOWERS_OFFSET +
+    REPO_OFFSET;
 
-  const FIRST_STEP = 0;
-  const SECOND_STEP = 5;
-  const THIRD_STEP = 20;
-  const FOURTH_STEP = 50;
-  const FIFTH_STEP = 130;
+  const RANK_S_VALUE = 1;
+  const RANK_DOUBLE_A_VALUE = 25;
+  const RANK_A2_VALUE = 45;
+  const RANK_A3_VALUE = 60;
+  const RANK_B_VALUE = 100;
+
+  const TOTAL_VALUES =
+    RANK_S_VALUE + RANK_A2_VALUE + RANK_A3_VALUE + RANK_B_VALUE;
 
   // prettier-ignore
   const score = (
@@ -27,26 +57,37 @@ function calculateRank({
     issues * ISSUES_OFFSET +
     stargazers * STARS_OFFSET +
     prs * PRS_OFFSET +
-    followers * FOLLOWERS_OFFSET
-  ) / totalRepos;
+    followers * FOLLOWERS_OFFSET + 
+    totalRepos * REPO_OFFSET 
+  ) / 100;
+
+  const normalizedScore = normalcdf(score, TOTAL_VALUES, ALL_OFFSETS) * 100;
 
   let level = "";
 
-  if (score == FIRST_STEP) {
-    level = "B";
-  } else if (score > FIRST_STEP && score <= SECOND_STEP) {
-    level = "B+";
-  } else if (score > SECOND_STEP && score <= THIRD_STEP) {
-    level = "A";
-  } else if (score > THIRD_STEP && score <= FOURTH_STEP) {
-    level = "A+";
-  } else if (score > FOURTH_STEP && score <= FIFTH_STEP) {
-    level = "A++";
-  } else if (score > FIFTH_STEP) {
+  if (normalizedScore < RANK_S_VALUE) {
     level = "S+";
   }
+  if (
+    normalizedScore >= RANK_S_VALUE &&
+    normalizedScore < RANK_DOUBLE_A_VALUE
+  ) {
+    level = "S";
+  }
+  if (
+    normalizedScore >= RANK_DOUBLE_A_VALUE &&
+    normalizedScore < RANK_A2_VALUE
+  ) {
+    level = "A++";
+  }
+  if (normalizedScore >= RANK_A2_VALUE && normalizedScore < RANK_A3_VALUE) {
+    level = "A+";
+  }
+  if (normalizedScore >= RANK_A3_VALUE && normalizedScore < RANK_B_VALUE) {
+    level = "B+";
+  }
 
-  return { level, score };
+  return { level, score: normalizedScore };
 }
 
 module.exports = calculateRank;
diff --git a/tests/calculateRank.test.js b/tests/calculateRank.test.js
@@ -13,6 +13,6 @@ describe("Test calculateRank", () => {
         prs: 300,
         issues: 200,
       })
-    ).toStrictEqual({ level: "S+", score: 192.13 });
+    ).toStrictEqual({ level: "A+", score: 49.16605417270399 });
   });
 });