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- slope1.d
- Tuesday, August 28th, 2007 at 11:41:48am MDT
- void init(T, U, V)(ref T[U] assoc, U where, lazy V how) {
- static assert(is(V: T));
- if (!(where in assoc)) assoc[where]=how;
- }
- struct slope1(I, U) { /// Items and Users
- struct userPrefs { U user; float[I] ratings; }
- float[I][I] diffs;
- size_t[I][I] freqs;
- void update(userPrefs[] prefs) {
- foreach (entry; prefs) foreach (item, rating; entry.ratings) {
- init(diffs, item, (float[I]).init);
- init(freqs, item, (size_t[I]).init);
- foreach (item2, rating2; entry.ratings) {
- init(diffs[item], item2, 0f);
- init(freqs[item], item2, 0);
- freqs[item][item2]+=1;
- diffs[item][item2]+=rating-rating2;
- }
- }
- foreach (item, ratings; diffs)
- foreach (item2, rating; ratings)
- ratings[item2]/=freqs[item][item2];
- }
- float[I] predict(userPrefs prefs) {
- float[I] preds; size_t[I] freqs;
- foreach (item, rating; prefs.ratings) {
- foreach (diffitem, diffratings; diffs) {
- if (!(diffitem in this.freqs) || (!(item in this.freqs[diffitem]))) continue;
- auto freq=this.freqs[diffitem][item];
- init(preds, diffitem, 0f);
- init(freqs, diffitem, 0);
- preds[diffitem]+=freq*(diffratings[item] + rating);
- freqs[diffitem]+=freq;
- }
- }
- float[I] res;
- foreach (item, value; preds) if (!(item in prefs.ratings) && freqs[item]>0) res[item]=value/freqs[item];
- return res;
- }
- }
- template constEnum(T, int start, S...) {
- static if(S.length)
- const char[] constEnum="const "~T.stringof~" "~S[0]~" = "~start.stringof~"; "~constEnum!(T, start+1, S[1..$]);
- else const char[] constEnum="";
- }
- import std.stdio;
- void main() {
- typedef int critters;
- mixin(constEnum!(critters, 0, "cuttlefish", "octupus", "squid", "nautilus"));
- typedef slope1!(critters, string) mySlope;
- mySlope s;
- s.update([
- mySlope.userPrefs("alice", [squid: 1f, cuttlefish: .5f, octupus: .2f]),
- mySlope.userPrefs("bob", [squid: 1f, octupus: 0.5f, nautilus: 0.2f]),
- mySlope.userPrefs("carole", [squid: .2f, octupus: 1f, cuttlefish: .4f, nautilus: .4f]),
- mySlope.userPrefs("dave", [cuttlefish: 0.9f, octupus: 0.4f, nautilus: 0.5f])
- ]);
- writefln(s.predict(mySlope.userPrefs("", [squid: 0.4])));
- }
- xt4100 ~/d $ gdc slope1.d -o slope1 && ./slope1
- [0:0.25,1:0.233333,3:0.1]
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