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Discussion Board -> Desktop Wallpaper, Art, etc. -> Official: c-index re-normalization

Official: c-index re-normalization

*caedes
07/13/04 8:08 PM GMT
In response to various design flaws in the system and sporatic abuse I've made some changes to the way the c-index is calculated.

cindex/100=1+e^(-favorites/10)*((downloads/views+2*rating)/3-1)

Where favorites has a maximum value of 10. This has the effect of making the number of favorites less important and weighing the rating (by voting) twice as much as the download to view ratio.
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-caedes

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::CaptainHero
07/13/04 8:26 PM GMT
Excellent, now we know the sacred formula

Will this affect all images?
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"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." Bertrand Russell
*caedes
07/13/04 8:39 PM GMT
It already has.
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-caedes
::CaptainHero
07/13/04 8:41 PM GMT
So I see from the other forums. Brilliant.
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"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." Bertrand Russell
noobguy
07/13/04 9:09 PM GMT
Very nice, the download to view ratio must be what causes newer images to have higher c-indexes, eh?
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A change in Point of View: 1 2 3 4 ... more to come. Ideas?
Si
07/13/04 10:34 PM GMT
Excellent idea! The fact that no matter how good an image was it couldn't score any more than quite a high proportion of the existing images seemed a bit unfortunate. We've all got a real incentive to try to get an image up there into those uncharted upper 90s now. Thank you from at least one satisfied customer ;-)
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+Samatar
07/13/04 11:25 PM GMT
I have a feeling this explanation would be more helpful if I could actually understand it... *wishes he had paid more attention to his maths teacher*
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-Everyone is entitled to my opinion-
::Torque
07/13/04 11:58 PM GMT
I like your redistribution Caedes, but I do have a suggestion. Perhaps you could devise an addition to the equation wherein as the number of views increases, the weight of the ratio of downloads/views decreases until it more or less disappears. I think that the age of an image will almost always be damaging to the downloads/views ratio, particularly if the image is ever a featured or top new image.

My images with mediocre ratings often maintain a higher downloads/views ratio then some of my images that became top new images, because the highest rated images are subject to viewing by more people. This particularly includes non-members who are more likely to view the info-page and never view images full screen. Also, as cookies expire (or whatever it is that causes subsequent views by the same member to eventually be counted again), members return to familiar images, follow up on comments, etc., and may not download the full screen view again.

Because of the nature of the site, it is feasible (and likely) to view without downloading, even if the picture is an excellent one, yet practically impossible to download without viewing (unless some shady linking is going on). So, even though it is technically possible to increase the views/downloads ratio over time (if every view is accompanied by a download), it is far more likely that this ratio will always decrease, particularly on the most popular images, and drag down their ratings.

I don't see anything wrong with incorporating this ratio upfront, but it's sort of a depressing notion that the ratings of all pictures will probably tend to decrease over time. As an alternative to phasing out the ratio, perhaps it could just be locked in after, say, 100 views or something. That way the older images would not have an advantage either. If you like the idea but would like me to make a formula suggestion, let me know and I will put my mind to it. Thanks for considering it and for constantly improving this site.

Josh
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~My select image - Wading Patiently
mimi5947
07/14/04 12:00 AM GMT
Me too Sam...*racking my brain for formula*....thank you for saying what I was going to say!
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Always, Mimi
noobguy
07/14/04 12:44 AM GMT
very well said torque, I like that this causes newer images to be placed on the top of the rankings (dont wanna see the same ones all the time) but with the new algorithm the scores are actually higher, not just better 99s, and the scores are much higher. Making it look like my new image is much "better" than my old image.
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A change in Point of View: 1 2 3 4 ... more to come. Ideas?
noobguy
07/14/04 12:59 AM GMT
No biggie though, no formula is perfect, you learn this early. On the plus side, I moved up quite a bit in the author list =D
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A change in Point of View: 1 2 3 4 ... more to come. Ideas?
::groo2k
07/14/04 12:35 AM GMT
This is great! In the past, with all of the 99s floating around, I would always think 'what's wrong with my image' if it got a 98...just kidding. Now, though, it'll be fun to chase an elusive 99...the quest begins. : )
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...rob... corp flag
blizzardboy
07/14/04 4:25 PM GMT
Hahah are there any 99's left?
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+WinterNight
07/14/04 8:33 PM GMT
Nope, its weird. Where there used to be pages and pages of 99s, there are no longer any 99-95s. The highest image is now a 94.
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-WinterNight
::TRACYJTZ
07/14/04 9:31 PM GMT
I personally love it this way. Thanks Caedes!
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noobguy
07/15/04 1:43 AM GMT
I've grown to enjoy the new algorithm, good job caedes.
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A change in Point of View: 1 2 3 4 ... more to come. Ideas?
::JOHANNA
07/15/04 5:18 AM GMT
Thanks Caedes you did a great job.
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Carpe diem.
PuMa
07/15/04 9:43 AM GMT
there goes my 99:100 images...
hehe

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** If you try to fail and you succeed, then which of the two did you do?
tgsgirl
07/15/04 10:32 AM GMT
I was sitting here sulking because I thought someone just gave all of my images a 1 or something :p
Even though it's not good for my pics, it's probably better this way
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Stuffed animals are always right
signpainter
07/15/04 12:17 AM GMT
Personally I like the the sudden change on the way the rankings are now, it was a little disturbing in the beginning with no notice from Caedes on what was going to happen and why. But I think Caedes has made a great move for everyone!
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Love your neighbor, it will drive 'em crazy!
signpainter
07/15/04 12:34 AM GMT
Inquiring minds wanna know...What is a good c-index rating now?...It surely can't be 99. Does anyone know?
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Love your neighbor, it will drive 'em crazy!
::Torque
07/15/04 12:43 AM GMT
All I can tell you Terry is that my highest images now are 90s. My images that were 99s are now in the 87-90 range. The highest images on the site seem to be in the mid-low 90s. This doesn't mean that anyone should vote differently than before (i.e. Oh, that image isn't a 10 because it isn't the best image on the site ever). The voting should be just the same, and the c-index will automatically be reduced to this new scale. If people stop giving out 10s all together because the best images are in the low 90s, the images will just fall even lower. I don't expect we'll see another 99, except maybe temporarily in the occasional brand new image (since in all the wonderful images on the site, not one 99 exists now). But, I think we'll all get used to the new scale, not a huge adjustment in my opinion :). It seems like an image in the upper 80s now is equivalent to a 99, and anything higher than that either has a distorted downloads/views ratio in its youth, or is just one outstanding image and has been voted very well.
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~My select image - Wading Patiently
signpainter
07/15/04 12:58 AM GMT
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Love your neighbor, it will drive 'em crazy!
signpainter
07/15/04 1:07 PM GMT
I agree Josh on the "We won't see many 99's if we see any at all" but now the way these changes were made seeing a 99 now is like hitting the lottery...hehe! I think seeing a 92 now is probably as close as it gets, I don't think I even have a 90 in my gallery, but I'm satisfied with these changes!
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Love your neighbor, it will drive 'em crazy!
PuMa
07/16/04 12:03 AM GMT
I agree.
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** If you try to fail and you succeed, then which of the two did you do?
::CaptainHero
07/16/04 9:36 AM GMT
This is definitely better.
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"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." Bertrand Russell
cemkarahan
07/16/04 7:47 PM GMT
Better this way.Now it is a lil' more realistic calculation.Nice job caedes thanks ;)
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Happiness is a behaviour.Sadness too.Make your mind CemKarahan
Winnter
07/16/04 11:22 PM GMT
Wow, am I ever glad I came across this discussion. My internet hasnt been working all that well so I haven't been around in awhile. Yesterday I checked all my images, and noticed how much my c-indexes had dropped. I couldn't figure out what happened. So thanks again for the explanation. It doesn't make me feel so bad now.
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** Nicky **
CSheridan10
07/18/04 12:11 AM GMT
ooh man, I am feeling some bad effects, My highest image is 78 where it was 95
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My image that needs some lovin'
signpainter
07/18/04 12:17 AM GMT
Have you been reading up Chris on what's going on? I'm sure everyone else feels that this is the way to go.
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Love your neighbors, it will drive 'em crazy!
co2metal
07/19/04 1:55 AM GMT
after the change, my image "articulation" emerges as one of the top few images on the entire site.. very strange
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When you come to a fork in the road, take it.
tbhockey
07/21/04 1:37 AM GMT
Dr. Caedes? hehe
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-tbhockey
postaldude66
08/13/04 11:41 PM GMT
I like these new changes, and although at first i was shocked my pride and joy 98:100 image had gone down to 81:100 i realised that the best images had all gone too. great new changes caedes, this means quality of high images should be really good.
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Neken
08/24/04 7:11 PM GMT
Sorry to drag this topic up again but.... ;)

First I'd just like to say that the change to the c-index system was needed as it was very top heavy. No problem with that at all.
Unfortunately though it does mean a new image can get hammered if it has a good first few hours and ends up on the front page. With no thumbnail available on the front page, many users will click on an image they have no interest in viewing and obviously not download it. The C-Index starts to plummet.

I really noticed this with my latest upload - The Observer*. Somehow it managed a 92 in the few hours from posting to the c-index update resulting in it being on the front page for a day. It went from a pretty usual ~50% view/download ratio to 15% (252/39)!
This clearly had a bit of a knock-on effect at the next c-index update. A drop to 71...

I know animal pics aren't the most popular images on here, but I assume the people who like them see the thumbnail and download them. Everyone else ignores them. On the front page this obviously can't happen.

Possible solutions:
1. The view/download to be made less significant to the c-index
2. New images are not put on the front page for e.g. 48-72 hours to allow the c-index to settle down and even out.
3. Thumbnails on the front page.

*edit: corrected image name...
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::noobguy
08/24/04 7:19 PM GMT
the thumbnails will possibly be changed in the next site design seeing has how this was a popular suggestion, but you would have to ask caedes. as for the first few hrs thing, I would suggest not posting right b4 the c-index gets calculated, thats all I can tell ya there :/
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An image rated way too low! Dragonfly Environment
::CaptainHero
08/24/04 7:26 PM GMT
I have looked at your image and it currently has a c-index of 81. That seems very reasonable to me.

I assume you are talking about the '6 new images' on the front page. I see what you are saying about there being no thumbnail, but I don't necessarily follow the reasoning. I can only speak for myself, but if I click on one of those, I invariably look at it full-size. If users are not doing this then that is a shame.

The revised c-index works well and I can't see it being changed. However, suggestion number 2 is maybe something to look at - I don't know what the current criteria for top new images is.

As for thumbnails on the front page, I don't think that would fit with the design - they would either be too small to properly see or large enough and therefore taking up too much precious room. The current design is going to change at some stage in the future (see here), but I don't see any provision for those thumbnails in the new design.

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"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." Bertrand Russell
Neken
08/24/04 7:38 PM GMT
Sorry - wrong image! (DOH! Knew I had this icon for some reason!)
I meant: The Observer. I'll edit my post....
As you can see on that image, a lot of people only view the description/comment page and don't download the full size image hence 252 views to 39 downloads.

I was thinking of the thumbnails with a view to the future design rather than this one. As you say it would be too cluttered.
Sorry about the mix-up!
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::noobguy
08/24/04 7:47 PM GMT
I think thumbnails would be a good addition to the front page, this was extrememly popularly accepted in the site design contest. And users who click on a top new image should not feel obligated to look at the full size. What if you are a photography fan and the image you click on is an extreme fractal art pick which you have no interest in whatsoever and you are on dial up. Should you feel obligated to look at the full size? this makes no sense. Also agree with both of you possibly about the number 2 suggestion.
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An image rated way too low! Dragonfly Environment
::CanoeGuru
08/24/04 10:05 PM GMT
I do think that you absolutely should look at the full size image if you are planning on casting a vote for that image. How can you acurately vote without viewing the image in the way it was intended? If you are not planning on casting a vote then of course you are not obligated to look at any image.
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"Even a fool is thought wise when he keeps his mouth shut."
::Torque
08/24/04 10:58 PM GMT
Matthew, I agree with your statement that people clicking on top new images and not viewing them full size is a shame, but unfortunately Neil is right. Invariably the top new images is a kiss of death. It's a great honor to have an image make that list, but it has always has a bitter after-taste since the changing of the c-index equation.

When I upload an image that is of a popular subject, best example being a sunet, it will typically start out with a views/downloads ratio above 90%. If the image turns out to be good enough to make the top new images list the next day, the views/downloads ratio will invariably fall into the 25%-33% range within one day on that list. Then the image will fall off the radar and go on to always have a much lower views/downloads ratio than an image that was qood, but never made it to the top new images list in the first place. The result is that the best of the best will generally have a lower c-index than the second-best of the best, so to speak. An image that appears for any length of time on the top-new images list will have a distinct disadvantage to one that does not, because approximatly 1/3 of the value that makes up its c-index--the views/downloads ratio--will be far below that of just about any image that never made the top new images list.

Neil gave one possible reason for this, the fact that people don't realize they're not interested in the image until they have already accounted for one view. I tend to think it is probably a result of the fact that far more visitors who are unfamiliar with the site will see the top new images, while the new images gallery is more of a place that members know to look for stuff they haven't seen before. And members are probably more likely to download the images they view, since first-time visitors may not even think to try.

It seems logical that the best, and most publicized images on the site will always have the worst views/downloads ratio because of all the newcomers who are likely to view them. I think that ratio is probably a poor indicator of the quality of the image and could be left out of the equation, but as it stands, it is the only factor that can reduce the c-index beyond the raw voting average. Since # of favorites folders the image is in can only improve the c-index, perhaps there could be some other factor with the power to reduce the c-index, although I can't think of one off-hand.

So, it's only my opinion but I think the views/downloads ratio is the only thing currently wrong with the c-index system, and I'm not sure if this has already been taken care of, but the last time I checked the image rankings, two of the top rated (by c-index) images on the site had views/downloads ratios larger than 1 (downloads > views), so there's obviously some funny-business with those images, and it obviously has a significant impact on the c-index. Just something to consider...
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~My select image - Wading Patiently
::CaptainHero
08/25/04 8:29 AM GMT
I think it is possible to have downloads > views if another site is hyperlinking directly to the large image, instead of the thumbnail page. I understand that Caedes is looking at introducing some code at some stage to try and counteract this.

With regard to thumbnails on the front page, perhaps this is what we need - Trisweb, redesign your new site! Alternatively, as a compromise, perhaps what we could have is a note of the category, just like on the 'featured image' i.e. 'computer->landscape' or whatever. This might ameliorate the effect of people clicking on the link and then finding it is a category they don't like.
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"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." Bertrand Russell
PuMa
08/25/04 9:14 AM GMT
Only thing I can say is that I agree with you Josh
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(<->.<(<->.<->)>.<->) They are watching you!
::stuffnstuff
10/03/04 4:56 AM GMT
With out superior knowledge of algebra or the tendencies of the masses on this site, can I make a suggestion? As I have mentioned in another discussion board, which I am too lazy to dig for :-), I believe that the adding of images to one's favorites gallery is under-valued. In my mind, a favorites gallery is there for people to show a little extra appreciation for an image if it is due, and also to tell something about themselves by revealing hwat they like in art. It seems that the value of an image being a favorite is ranked towards those who dub one a favorite just if they like it, if it looks difficult to make, or on impulse. This is not a bad thing, but a perfect example would be Bethany. It is understandable to have a large favorites gallery for thsoe who have been here a long time, but if the number gets excessive, it isn't effective to show this extra step. I do my best to keep my favorites gallery contained in a single page, which is a lot to ask for some, but could there be a page limit for all users, like maybe 5 pages? (I, for one, won't look through 26 pages because I am bored!) Is this realistic, and can the formula be adjusted towards this if such changes are made? Please reveal the sides of my argument that I am blind towards. Thanks.


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-those who hit rock bottom are too concerned with self pity to realize that they are lying on an anvil- Psalm 66:10, Job 10:8
::noobguy
10/03/04 2:26 PM GMT
dont see that happening, bethany's page is small compared to others, in fact its average compared to alot of the older members, who have favorites spanning back into the beginnings of the site. The favorites is not valued as much because it is abused as you pointed out instead of valued. But at the same time with +12,500 images on the site, even 5 pages may be asking too much for some people. The only way for some people to maintain these few images in their favorites gallery would be to recycle, delete old ones to make space for new favorites. When you remove an image from favorites, as far as I know, the c-index drops, therefore, the c-index of old images would be hurt by this limit no?
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The easiest way to miss a shot is to not venture far enough to find it.
::stuffnstuff
10/04/04 1:59 AM GMT
It probably would (hurt old images), but as a compensation for those select few, it would rise. If not 5, then 10? I have seen some pretty rediculous numbers, but 26 was the largest I could find on short notice. When I really like an image and add it to my favorites gallery, I generally find another to take off so I don't pass my personal limit, and if I had commented that I added it to my favorites, I simply edit it out. If users "abuse" the favorites, it becomes just another way of voting slightly higher, and in my mind it shows less respect for an image. Does anyone agree? Is it worth the hassle?
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-those who hit rock bottom are too concerned with self pity to realize that they are lying on an anvil- Psalm 66:10, Job 10:8
::noobguy
10/04/04 2:29 AM GMT
i've seen mid 20s quite a bit, thats not that much at all, i've seen up in the 30s a few times
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The easiest way to miss a shot is to not venture far enough to find it.
::CaptainHero
10/05/04 10:33 PM GMT
I have 4 pages and that is plenty. 26 pages is sheer madness & that user has only been on the site since June! A 5 page limit is more than enough.

The whole problem as usual is restraint - users just can't stop giving 10's, adding favorites and uploading way too many images.
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"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." Bertrand Russell

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