southwolf · January 21, 2019 03:14 · Dec 30, 2015 · Dec 30, 2015 · Dec 29, 2015 · Dec 28, 2015
diff --git a/stats.js b/stats.js
@@ -1,4 +1,5 @@
- /* jshint node: true */
+#!/usr/bin/env node 
+/* jshint node: true */
 'use strict';
 var program = require('commander');
 
@@ -92,27 +93,23 @@ function getZPercent(z)
     return sum;
 }
 
-function example(){
-  var i = 100;
-  do{
-      var x = Math.round(Math.random() * 1000) + 1;
-      var rnd_arr = randomArrayThousand(99);
-      var std = stdDev(rnd_arr);
-      var zscr = zScore(x, average(rnd_arr), std);
-      var zp = getZPercent(zscr);
-      console.log("The Standard Deviation of a random 100 elements Array [Values 1:1000] is: " + std );
-      console.log("zScore of random X="+ x +" is: " + zscr);
-      console.log("Percentile: " + Math.floor(zp * 100) + "%" );
-      console.log("Median: " + median(rnd_arr));
-
-      i--;
-  } while (i > 0);
+function example(n){
+  n = typeof n !== 'undefined' ? n : 100;
+  var x = Math.round(Math.random() * 1000) + 1;
+  var rnd_arr = randomArrayThousand(n);
+  var std = stdDev(rnd_arr);
+  var zscr = zScore(x, average(rnd_arr), std);
+  var zp = getZPercent(zscr);
+  console.log("The Standard Deviation of a random " +n+ " elements Array [Values 1:1000] is: " + std );
+  console.log("zScore of random X="+ x +" is: " + zscr);
+  console.log("Percentile: " + Math.floor(zp * 100) + "%" );
+  console.log("Median: " + median(rnd_arr));
 }
 
 program
   .version('0.0.1')
   .description('An Application to Calculate Descriptive Statistics')
-  .option('-e, --example', 'Execute Example Code')
+  .option('-e, --example <n>', 'Execute Example Code')
   .parse(process.argv);
 
-if (program.example) example();
+if (program.example) example(program.example);
diff --git a/stats.js b/stats.js
@@ -1,4 +1,3 @@
-#!/usr/bin/env node
  /* jshint node: true */
 'use strict';
 var program = require('commander');
@@ -15,29 +14,29 @@ function numSquare(a) {
   return Math.pow(a, 2);
 }
 
-function randomArrayThousand(numElems){
+function randomArrayThousand(numElems) {
     var arr = [];
     for (var i=0; i<numElems; i++){
         arr.push(Math.round(Math.random() * 1000) + 1);
     }
     return arr;
 }
 
-function average(arr){
-    var sum = arr.reduce(add);
-    return sum / arr.length;
-}
-
 function median(arr) {
     arr.sort(numericSort);
     if (arr.length % 2 === 0){
       return arr[arr.length/2];
     }
     else{
-      return (arr[arr.length/2 - 1] + arr[arr.length/2]) / 2;
+      return (arr[Math.floor(arr.length/2 - 1)] + arr[Math.floor(arr.length/2)]) / 2;
     }
 }
 
+function average(arr){
+    var sum = arr.reduce(add);
+    return sum / arr.length;
+}
+
 function deviations(arr, mean){
     return arr.map(function(a, mean) { return a - mean});
 }
@@ -97,12 +96,14 @@ function example(){
   var i = 100;
   do{
       var x = Math.round(Math.random() * 1000) + 1;
-      var rnd_arr = randomArrayThousand(100);
+      var rnd_arr = randomArrayThousand(99);
       var std = stdDev(rnd_arr);
       var zscr = zScore(x, average(rnd_arr), std);
       var zp = getZPercent(zscr);
-      console.log(i + " - The Standard Deviation of a random 1000 Array [1 - 100] is: " +
-          std + " zScore of X="+ x + ": " + zscr + " Percentile: " + Math.floor(zp * 100) + "%" );
+      console.log("The Standard Deviation of a random 100 elements Array [Values 1:1000] is: " + std );
+      console.log("zScore of random X="+ x +" is: " + zscr);
+      console.log("Percentile: " + Math.floor(zp * 100) + "%" );
+      console.log("Median: " + median(rnd_arr));
 
       i--;
   } while (i > 0);

diff --git a/stats.js b/stats.js
@@ -1,3 +1,4 @@
+#!/usr/bin/env node
  /* jshint node: true */
 'use strict';
 var program = require('commander');
@@ -6,6 +7,10 @@ function add(a, b){
   return a + b;
 }
 
+function numericSort(a,b) {
+    return a - b;
+}
+
 function numSquare(a) {
   return Math.pow(a, 2);
 }
@@ -23,6 +28,16 @@ function average(arr){
     return sum / arr.length;
 }
 
+function median(arr) {
+    arr.sort(numericSort);
+    if (arr.length % 2 === 0){
+      return arr[arr.length/2];
+    }
+    else{
+      return (arr[arr.length/2 - 1] + arr[arr.length/2]) / 2;
+    }
+}
+
 function deviations(arr, mean){
     return arr.map(function(a, mean) { return a - mean});
 }
@@ -32,7 +47,7 @@ function squaredDeviations(arr){
     // return arr.map(function(a){ return Math.pow(a, 2)});
 }
 
-function varianceExample(arr){
+function variance(arr){
 
     var avg = average(arr);
     return squaredDeviations(deviations(arr, avg)).reduce(add) /  arr.length;
@@ -41,7 +56,7 @@ function varianceExample(arr){
 function stdDev(arr, sample){
     // default value of sample is false. If sample is defined then we apply Bessel's Correction.
     sample = typeof sample !== 'undefined' ? sample : false;
-    return sample ? Math.sqrt(varianceExample(arr)) - 1 : Math.sqrt(varianceExample(arr));
+    return sample ? Math.sqrt(variance(arr)) - 1 : Math.sqrt(variance(arr));
 }
 
 function zScore(x, m, std){

diff --git a/stats.js b/stats.js
@@ -0,0 +1,102 @@
+ /* jshint node: true */
+'use strict';
+var program = require('commander');
+
+function add(a, b){
+  return a + b;
+}
+
+function numSquare(a) {
+  return Math.pow(a, 2);
+}
+
+function randomArrayThousand(numElems){
+    var arr = [];
+    for (var i=0; i<numElems; i++){
+        arr.push(Math.round(Math.random() * 1000) + 1);
+    }
+    return arr;
+}
+
+function average(arr){
+    var sum = arr.reduce(add);
+    return sum / arr.length;
+}
+
+function deviations(arr, mean){
+    return arr.map(function(a, mean) { return a - mean});
+}
+
+function squaredDeviations(arr){
+    return arr.map(numSquare);
+    // return arr.map(function(a){ return Math.pow(a, 2)});
+}
+
+function varianceExample(arr){
+
+    var avg = average(arr);
+    return squaredDeviations(deviations(arr, avg)).reduce(add) /  arr.length;
+}
+
+function stdDev(arr, sample){
+    // default value of sample is false. If sample is defined then we apply Bessel's Correction.
+    sample = typeof sample !== 'undefined' ? sample : false;
+    return sample ? Math.sqrt(varianceExample(arr)) - 1 : Math.sqrt(varianceExample(arr));
+}
+
+function zScore(x, m, std){
+    return Math.abs(x - m) / std;
+}
+
+function getZPercent(z)
+{
+    // http://stackoverflow.com/questions/16194730/seeking-a-statistical-javascript-function-to-return-p-value-from-a-z-score
+    //z == number of standard deviations from the mean
+
+    //if z is greater than 6.5 standard deviations from the mean
+    //the number of significant digits will be outside of a reasonable
+    //range
+    if ( z < -6.5)
+        return 0.0;
+    if( z > 6.5)
+        return 1.0;
+
+    var factK = 1;
+    var sum = 0;
+    var term = 1;
+    var k = 0;
+    var loopStop = Math.exp(-23);
+    while(Math.abs(term) > loopStop)
+    {
+        term = 0.3989422804 * Math.pow(-1,k) * Math.pow(z,k) / (2 * k + 1) / Math.pow(2,k) * Math.pow(z,k+1) / factK;
+        sum += term;
+        k++;
+        factK *= k;
+    }
+    sum += 0.5;
+
+    return sum;
+}
+
+function example(){
+  var i = 100;
+  do{
+      var x = Math.round(Math.random() * 1000) + 1;
+      var rnd_arr = randomArrayThousand(100);
+      var std = stdDev(rnd_arr);
+      var zscr = zScore(x, average(rnd_arr), std);
+      var zp = getZPercent(zscr);
+      console.log(i + " - The Standard Deviation of a random 1000 Array [1 - 100] is: " +
+          std + " zScore of X="+ x + ": " + zscr + " Percentile: " + Math.floor(zp * 100) + "%" );
+
+      i--;
+  } while (i > 0);
+}
+
+program
+  .version('0.0.1')
+  .description('An Application to Calculate Descriptive Statistics')
+  .option('-e, --example', 'Execute Example Code')
+  .parse(process.argv);
+
+if (program.example) example();
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