[r-t] Blue Line Difficulty

King, Peter R peter.king at imperial.ac.uk
Tue Aug 29 18:44:53 UTC 2017

Since I was attributed with raising the question in the first place I guess I should respond.

The context of why I asked the question (I think) was that we had rung some peals of ATW plain major and treble bob major and these proved to be quite challenging for the very experienced bands ringing them (I hope the members of the bands don't mind my description of this). So it got me wondering why some things were "harder" than others. In those cases I think it was just the volume of new stuff that had to be learnt. Most surprise major methods are made up for bits of work that are fairly familiar, but with the occasional bit of new stuff. With treble bob methods, for example, you don't have things like Yorkshire places, or long London, or fishtails. You have new structures to learn. With plain methods you don't have the luxury of a dodge with the treble to try to remember what you are doing next. So I concluded that difficulty, in this context, was basically familiarity. It is easy to learn a new surprise method if you know a fair number already, because it is almost certainly a bit of that connected to a bit of this in some way.

So I lost interest in the idea, or rather I don't think difficulty is the right terminology. Other than the coarse grained system that Don and Graham mention here I would agree that quibbling over whether a 4.9 difficulty method is harder or easier than a 5.0 difficulty index one is a bit pointless as it is so subjective. Complexity is a different issue. Graham has proposed a measure of complexity (Method Master has another one). It is certainly possible to define measure of complexity in all sorts of ways. A blue line is, after all, a time series and you can do all sorts of thing like those (look at the Fourier components for example to tell you whether you are basically just hunting backwards and forwards or there is lots of small frequency stuff). I don't know if that is remotely interesting or not. I think there is some value in having a crude estimate of this so if you are looking at new methods then you have some way of telling whether or not your band could be up to it. I would suggest there should be a different index for handbells as tower bells Beverley and Surfleet are much harder in hand than in the tower.

Another measure that I like the thought of is what happens if you go wrong. If you miss a dodge in plain bob you just end up at the front (or back) a few blows early which is easy to sort out. In other methods getting one blow out soon gets you to the wrong end of the change. So perhaps a measure of the divergence of blue line would be interesting (like the Lyapunov exponent for chaotic systems). These are just random musings. I agree with the general consensus that "difficulty" per se is a very subjective and ill defined concept. Some measure of complexity could be defined, whether it is useful or not is unclear.

-----Original Message-----
From: ringing-theory [mailto:ringing-theory-bounces at bellringers.org] On Behalf Of Graham John
Sent: 29 August 2017 17:36
To: ringing-theory at bellringers.org
Subject: Re: [r-t] Blue Line Difficulty

On 29 August 2017 at 16:04, Don Morrison <dfm at ringing.org> wrote:

> We need just a few suitably sized buckets to drop methods into, with 
> the explicit recognition that the borders between neighboring buckets 
> are not clear.

That's exactly what I was thinking of doing. I need a metric to assign buckets, which can be split into blue line complexity of very low; low; medium; high; very high.


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