What rating value can be considered the "middle" of the rank?

Is there more distance between 1 kyu and 1 dan compared to all other ranks?

AGA uses a system where negative values represent kyu ranks and positive values represent dan ranks. They also state that the middle of a rank is at the .5 mark of that number. For example, -3.5 = a true 3 kyu whereas -3.0 is actually halfway between 3 kyu and 2 kyu. Because of the nature of this system, you cannot be any rating that is between -1.0 and 1.0. -1.0 and 1.0 are essentially equal as they represent the halfway point between 1 kyu and 1 dan.

But on OGS I noticed that people can have 0.5d or 0.8k rankings. This seems problematic to me because it would increase the distance between 1 kyu and 1 dan no matter how you slice it. If you consider 1.5k to be the middle of 1 kyu and 1.5d to be the middle of 1 dan, that’s 1.5 in either direction of 0, resulting in a full 3 points of rating gap. Compare this to the difference between 1.5k and 2.5k, which is only 1 point.

Okay, then let’s consider the alternative and decide that 1.0k is the true middle of 1 kyu and 1.0d is the true middle of 1 dan. This still results in a doubled amount between these two ranks because they are 1 point away from zero in opposite directions. Again, compare this to the difference between 1.0d and 2.0d for example – only 1 point of difference.

So my question is, what is considered the middle of each rank, and is there something that accounts for this problem that arises from the fact that there is no such thing as 0 kyu or 0 dan?

How is the “overall” rating calculated?

Another question I had is about how the “overall” rating is calculated. I understand from this comment that each rating in the table are separate calculations using unique pools of data. Does this mean the “overall” rating is calculated from all games played indiscriminately? Meaning, if I am an expert 9x9 player who can play at a 1 dan level but have no concept of fuseki on a 19x19, I’ll be matched with a dan level player until my rating inevitably tanks?

Finally, how is the number beside my name decided? I am 4.1k on my actual rating number but it displays [5k]. If anyone can help answer these questions, I’d really appreciate it.

Win a game and become 4.0 or 3.9 kyu and the display will be [4k].

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Internally the ranks are just numbers, where 0 is the border between Kyu and Dan. To get the integer rank, this number is rounded away from 0. In this sense all ranks have the same distance.

-0.1 → 1k
0.1 → 1d

The middle point on each rank window is X.5 without skipping any.


OGS aims for a rank distance of 1 stone handicap between adjacent ranks. In this sense there distance between ranks stays the same.
Since an additional stone is more worth on higher ranks, the win rate distance increases for higher ranks steadily (for games without handicap).

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Oh… okay so that would mean 0.5k is kind of the middle of 1 kyu, 1.5k is the middle of 2 kyu, etc. And I can also guess with this system the lowest rank possible is 25.0k. That makes sense, though not intuitive since your rating number will almost always look like a lower value than the traditional “kyu/dan” number. But I think I got it… thanks for clearing that up!

Going off topic now …

Intuitive means “using or based on what one feels to be true even without conscious reasoning; instinctive.”

When you were taught about the rules and more of go, a rank system was explained to you. You adopted that system as your own. Should you not have been raised with the AGA model, but with another model, you probably would have experienced AGA as not intuitive. :grinning:

My intuition probably differs from yours, because in my opinion intuition is mostly a learned phenomenon.

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From this picture,
ScreenShot_14_04_2023_10_29_23
your rating is 1607 and your rank is 5k but quite close to 4k.

According to 2021 Rating and rank adjustments the conversion formula from rating to rank is ln(rating / 525) * 23.15.
If ln(rating / 525) * 23.15 is between 0 and 1 you are 30k
If it is between 1 and 2 you are 29k

If it is between 25 and 26 you are 5k

If it is between 29 and 30 you are 1k
If it is between 30 and 31 you are 1d

In your case ln(rating / 525) * 23.15 = 25.9. This is between 25 and 26 so you are 5k. Since this is less than 0.1 rank below the 4k threshold, this explains why “4.1k” is displayed.

In my case
ScreenShot_14_04_2023_10_45_25
ln(rating / 525) * 23.15 = 30.95
This is between 30 and 31 so I am 1d, but less than 0.1 rank below the 2d threshold which explains why 1.9d is displayed.

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Well, “being raised” on the AGA model is worded a bit strongly, I only learned of it this past year. Intuition is not learned. A blue switch controlling a blue light and a yellow switch controlling a yellow light is intuitive. I just find it more intuitive for the numbers to match the ranks.

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I’ll take this as the reason why I can’t reach and stay at 1d - the gap is too big from 1kyu :smiley:

I think you can play around with ratings to rank calculations interactively here as well Play Go at online-go.com! | OGS . You don’t have to mess with everything, just play around with the rating box and it should update the rank

image

I think in lower ranks ~15kyu or so, it looks like it’s about 50 rating points gaps between ranks. Then around 5kyu = 1550 ish it’s starts to become a bit wider, 1620 ~ 4kyu, 1690~3kyu and 1760~2kyu so about 70 rating points gap.

Now 1840~ 1kyu so 80 points gap, and same to 1920 ~ 1dan. For 2dan upward it’s actually like a gap of about 90 up to about 4dan.

Then it’s like 100 points to get to from 4d to 5d at 2290, and similar to about 7dan at 2490, like 110 to get to 8d at 2600 and then I think 120 to 9dan.

So the gaps in rating points do increase as you go up, and there is a slightly larger gap around 1kyu-1dan than in lower ratings gaps say.

I never really payed attention to it before but this seems to make sense.

Sorry to bump this thread but I noticed something and I’m confused again.

I am 4.2k and I am displayed as [5k], which made sense after it was explained to me.

However, this player’s overall rating is 2.5d and they are showing as [2d].

As @flovo stated:

Internally the ranks are just numbers, where 0 is the border between Kyu and Dan. To get the integer rank, this number is rounded away from 0. In this sense all ranks have the same distance.

-0.1 → 1k
0.1 → 1d

By this logic,
1.1 → 2d
2.1 → 3d

So shouldn’t that player display as [3d]?

It’s just a convention. You jump directly from 0.0k to 1.0d. There is no 0.5d.

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Ohh I could have sworn I saw a 0.5d rank somewhere but this makes a lot more sense. Thank you!

I agree completely, that player should display as 3d.

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:joy::joy::joy::joy: hi