CHART: How many courses are available on Duolingo?
As someone who absolutely loves learning foreign languages, I wanted to see which languages Duolingo offers courses in.
So, here's a chart to show the relation between the courses available for the native languages. The key is underneath to describe the relation for each course for November 06, 2017.
NB: This chart is ONLY for the courses shown on the Languages Courses page on Duolingo; I decided not to indicate the ones in the Incubation page.
Purple — Courses offered for BOTH native languages. (Ex. English > Spanish, Spanish > English)
Red — Courses offered for ONE native language. (Ex. Thai > English, English > Ø)
Green — Unique language courses for languages WITHOUT courses for native speakers. (Ex. Spanish > Catalan, Catalan > Ø)
Blue — Language courses presently offered for one language and in development for the other. Box will turn PURPLE upon reaching Beta. (Ex. Chinese > English, English > Chinese [IN DEVELOPMENT])
Pink — Developing One-Way Course Language courses NOT IN BETA on the Language Courses Page. (Ex. Tamil > English)
Its interesting that the only two courses one can't do from english are Catalan and Guaraní. And I wonder down the road what other languages will come not from english first, and later but I am not focusing on that. Ketchwa/Kitchwa could make sense to do from Spanish, came with Nauhatl, even Basque. There are a bunch of Mayan languages, but I don't really see those being added to this platform, not even really long term. I am sure their are more to think of, and I am primarily thinking of from Spanish because that is a language I know.
These are the longest continuous ladders I could find, the current max seems to be 8 courses:
Longest Current Ladder, 8 courses:
(Other)-> English-> (Russian/Turkish)-> German-> French-> Portuguese-> Italian-> Spanish-> (Catalan/Guarani/Esperanto)
If we include courses that are in-development, the chain can be extended to 9. I couldn't find any way to reach 10 from these, but I think there are courses in the Incubator not included in your chart, and it might be possible if those are taken into account.
Longest In-Development Ladder, 9 courses:
(Other)-> English-> Turkish-> Russian-> German-> French-> Portuguese-> Italian-> Spanish-> (Catalan/Guarani/Esperanto)
This sheet, and the one by the OP are both not up to date.
I think a graph/network/web would show the relations the best, but this link is the next best.
Edit: it should be mostly up to date now, except for some numbers and courses in phase 1 incubation.
Edit2: I found this https://forum.duolingo.com/comment/37677398, it's in the form of a language 'web'.
So, your chart idea inspired me to make one on the potential for inter-language laddering on Duolingo, which I just drew and is quite neat. There 8 languages one can cycle through, and 4 options that dead end outside of all the english courses, excluding Esperanto (these are catalan, Guaraní, and esperanto from english and Spanish. Though I didn't include these in my depiction, because while they can be laddered courses, they can't be inter-language laddered.
Its kind of fun, because one can plot and draw what level of laddering one is at, and where on can go to. Like there are terms for different types of laddering moves.
Level 1 Laddering—(Base) or Native Language (Base Language) to New Language 1
Level 1 Reverse Course—New Language 1 to Native Language
Level 2— Language 1 Learned to New Language 2 Learned
Level 2 Reverse Course—New Language 2 to Language 1 learned
Level 3—Language 2 Learned to New Language 3
Level 3 Reverse Course— New Language 3 to Language 2 Learned
3 to 1— New Language 3 to Base or Native Language
1 to 3 (Technically just Level 2 laddering, but slightly different clasifacation)—Base Language to New Language 3.
And so on....It is kind of a neat concept. I have done Spanish to PTGS (what I consider Level One essentially). Spanish to Portuguese (Level one reverse course). Portuguese to French (Level 2. Not completed). French 2 Portuguese (Level 2 reverse course. Not completed). Spanish to French (level 1. Not completed). Portuguese to Italian (Level 2).
And there is just a string of other different kind of modelings and terminology one can apply. The most unique laddering string, I think goes through Russian and Turkish, which already have some of the uniquest routes, and will have more when Turkish can go to Russian—soon—and Russian can go to Swedish. But even on there own right now, learning German from Turkish, or going from Russian to one of the 4 options seems like a stark challenge.
Kind of fun idea I came up with for modeling routes for inter-language laddering with some terminology.