Another quasimetric! Actually a pseudo-quasi-metric. Facebook’s news feed decides what status updates to show you based on three factors:

1. affinity u — how much you like somebody (FB’s guess)
2. type of post w — videos and photos are more interesting than “Chris liked Lili’s status update”
3. time since post d — show newer stuff

$\dpi{200} \bg_white \sum_\mathrm{graph} \scriptstyle \text{affinity}_e \; \cdot \scriptstyle \text{ type}_e \; \cdot \scriptstyle \text{ time decay}_e$

The affinity score is a pseudoquasimetric — it’s a one-way measure. If I’m always looking at your profile because you’re a fascinating girl that I met at a party and have been stalking ever since, your updates will show up more in my feed.

But, say you’re the girl and you didn’t think I was interesting at all and never looked at my profile after you Accepted my offer of internet-ual befriendship, my stories won’t be interesting to you and are unlikely to be displayed.

In other words, stalkers don’t show up in your news feed.

The properties of a quasimetric, again, are:

1. never below zero
2. the only “distance of zero” is the distance of something to itself
3. dist( ①→③ )  ≤   dist( ①→② )   +   dist( ②→③ )

Had to drop the second one because there might be lots of FB friends Ⓑ,Ⓒ,Ⓓ,Ⓔ who are not important to me Ⓐ and thus dist( Ⓐ→Ⓑ ) = 0 | Ⓐ≠Ⓑ. (But maybe not?)

Anyway, I threw a "pseudo" on the "quasimetric" just in case lots of different people are of zero interest.

Math news out.

13 notes

1. geeksngamers reblogged this from isomorphismes
2. compendious reblogged this from isomorphismes and added:
Explains why stalkers don’t show up in your newsfeed …
3. becauseducks reblogged this from isomorphismes
4. isomorphismes posted this