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December 25, 2012 05:45
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/** | |
* A little code from Collective Intelligence translated to javascript | |
*/ | |
var critics = { | |
"Lisa Rose": { | |
"Lady in the Water" : 2.5 | |
, "Snakes on a Plane" : 3.5 | |
, "Just My Luck" : 3.0 | |
, "Superman Returns" : 3.5 | |
, "You, Me and Dupree" : 2.5 | |
, "The Night Listener" : 3.0 | |
}, | |
"Gene Seymour": { | |
"Lady in the Water" : 3.0 | |
, "Snakes on a Plane" : 3.5 | |
, "Just My Luck" : 1.5 | |
, "Superman Returns" : 5.0 | |
, "The Night Listener" : 3.0 | |
, "You, Me and Dupree" : 3.5 | |
}, | |
"Michael Phillips": { | |
"Lady in the Water" : 2.5 | |
, "Snakes on a Plane" : 3.0 | |
, "Superman Returns" : 3.5 | |
, "The Night Listener" : 4.0 | |
}, | |
"Claudia Puig": { | |
"Snakes on a Plane" : 3.5 | |
, "Just My Luck" : 3.0 | |
, "The Night Listener" : 4.5 | |
, "Superman Returns" : 4.0 | |
, "You, Me and Dupree" : 2.5 | |
}, | |
"Mick LaSalle": { | |
"Lady in the Water" : 3.0 | |
, "Snakes on a Plane" : 4.0 | |
, "Just My Luck" : 2.0 | |
, "Superman Returns" : 3.0 | |
, "The Night Listener" : 3.0 | |
, "You, Me and Dupree" : 2.0 | |
}, | |
"Jack Matthews": { | |
"Lady in the Water" : 3.0 | |
, "Snakes on a Plane" : 4.0 | |
, "The Night Listener" : 3.0 | |
, "Superman Returns" : 5.0 | |
, "You, Me and Dupree" : 3.5 | |
}, | |
"Toby": { | |
"Snakes on a Plane" : 4.5 | |
, "You, Me and Dupree" : 1.0 | |
, "Superman Returns" : 4.0 | |
} | |
}; | |
function simDistance (prefs, person1, person2) { | |
var si = {} //shared items | |
, p1Prefs = prefs[person1] | |
, p2Prefs = prefs[person2] | |
; | |
for (var item in p1Prefs) | |
if (p2Prefs[item]) | |
si[item] = 1; | |
if (Object.keys(si).length == 0) | |
return 0; | |
var sumOfSquares = 0; | |
for (var sharedItem in si) | |
sumOfSquares += Math.pow(p1Prefs[sharedItem] - p2Prefs[sharedItem], 2); | |
return 1 / (1 + Math.sqrt(sumOfSquares)); | |
} | |
function simPearson (prefs, person1, person2) { | |
var si = {} //shared items | |
, p1Prefs = prefs[person1] | |
, p2Prefs = prefs[person2] | |
; | |
for (var item in p1Prefs) | |
if (p2Prefs[item]) si[item] = 1; | |
var n = Object.keys(si).length; | |
if (n == 0) return 0; | |
var sum1 = 0, sum2 = 0, sum1Sq = 0, sum2Sq = 0, pSum = 0; | |
for (var it in si) { | |
var p1 = p1Prefs[it], p2 = p2Prefs[it]; | |
sum1 += p1; | |
sum2 += p2; | |
sum1Sq += Math.pow(p1, 2); | |
sum2Sq += Math.pow(p2, 2); | |
pSum += p1 * p2; | |
} | |
var num = pSum - (sum1 * sum2 / n); | |
var den = Math.sqrt((sum1Sq - Math.pow(sum1, 2) / n) * (sum2Sq - Math.pow(sum2, 2) / n)); | |
if (den == 0) return 0; | |
return num / den; | |
} | |
function topMatches (prefs, person, n, similarity) { | |
n = n || 5; | |
similarity = similarity || simPearson; | |
var results = []; | |
for (var other in prefs) | |
if (other != person) | |
results.push([other, similarity(prefs, person, other)]); | |
results.sort(function (a, b) { return b[1] - a[1] }); | |
results = results.splice(0, n); | |
return results; | |
} | |
function getRecommendations (prefs, person, similarity) { | |
similarity = similarity || simPearson; | |
var totals = {}, simSums = {}; | |
for (var other in prefs) { | |
if (person == other) continue; | |
var sim = similarity(prefs, person, other); | |
if (sim <= 0) continue; | |
for (var item in prefs[other]) { | |
if (!prefs[person][item] || prefs[person][item] == 0) { | |
if (!totals[item]) totals[item] = 0; | |
if (!simSums[item]) simSums[item] = 0; | |
totals[item] += prefs[other][item] * sim; | |
simSums[item] += sim; | |
} | |
} | |
} | |
var rankings = []; | |
for (var item in totals) { | |
var total = totals[item]; | |
rankings.push([item, total/simSums[item]]); | |
} | |
rankings.sort(function (a, b) { return b[1] - a[1] }); | |
return rankings; | |
} | |
function transformPrefs (prefs) { | |
var results = {}; | |
for (var person in prefs) { | |
for (var item in prefs[person]) { | |
if (!results[item]) results[item] = {}; | |
results[item][person] = prefs[person][item]; | |
} | |
} | |
return results; | |
} | |
function calculateSimilarItems (prefs, n) { | |
n = n || 10; | |
var result = {}; | |
var itemPrefs = transformPrefs(prefs); | |
var c = 0; | |
for (var item in itemPrefs) { | |
c += 1; | |
if (c % 100 == 0) console.log(c, ' / ', Object.keys(itemPrefs).length); | |
var scores = topMatches(itemPrefs, item, n); | |
result[item] = scores; | |
} | |
return result; | |
} | |
module.exports.critics = critics; | |
module.exports.simDistance = simDistance; | |
module.exports.simPearson = simPearson; | |
module.exports.topMatches = topMatches; | |
module.exports.getRecommendations = getRecommendations; | |
module.exports.transformPrefs = transformPrefs; | |
module.exports.calculateSimilarItems = calculateSimilarItems; |
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