Hello poppets! As my nephew Jimbo said, I'm just back from a river cruise of Europe where I had many nautical adventures! Quite different to ocean cruising experiences where I hear there's sea men everywhere. I, on the other hand, saw rather a lot of my butler, Reginald. I don't think there was a lot of "sea man" in Reginald to be perfectly frank. Ill-natured fellow, always dropping around to announce the tea, or dinner and so on in a very unpleasant way. I was a bit taken aback by his testy calls initially, but I got used to them as time went on. We even shared a glass of vintage Bordeaux on the last evening of the cruise - there's nothing like a full-bodied '69 on the cabin balcony during sunset, don't you think?

Well, enough chit chat! Let's get down to business.

"Probed" in Kansas writes:

My general advice to anyone who sees a spaceman is to park in it, man. Oh haha! Now seriously my very strong suggestions to you are: (1) Do not shave drunk; and (2) Throw away your styptic pencil as I rather suspect it's boldly gone where no man has gone before.

Well that's it for now my poppets! Remember, if you have a question for Aunty Jimbo contact me c/o Jimbo's Blog Comments page! Hooroo!

Aunty Jimbo. xxx ]]>

It could well be imagined that for many the very idea that random behaviour plays any kind of role in the area of shaving is complete anathema. This is, by necessity, a very deterministic hobby and no one wants to think that the outcome of their daily shave is dependent on the vagaries of chance. However, when we consider the role of randomness we are not talking about gross outcomes, but rather the variations that occur at an individual level - to the inputs to the shave as it were. We are talking about the "YMMV" (Your Mileage May Vary) component that is present both between shavers and between shaves.

Take for example the circumstance of cutting or nicking oneself. It is a rare event to read someone post "Yes, I deliberately set out to cut my face this morning" (though based on some of the techniques I have seen people use over the years, this would be an honest comment to make....!! :)). No, a nick or cut is most definitely not a deterministic event and therefore both the event itself and the component events that lead up to it must be considered as random.

Moreover, we are not robots. We do not have the ability, no matter how hard we try, to exactly replicate shaves: identical angles at identical times at identical places on the face with identical pressures, identical amount of soap applied to brushes with identical amounts of water in them etc. The whole idea is ridiculous. Similarly with honing, stropping, prep. and so on. We vary. We vary from each other, and we vary within ourselves. Some of this variation can be explained in deterministic ways - these are often the topics of discussion in the forums: technique, blade type, lather, prep etc. However, this variation both within and between shavers also has a distinct and non-trivial component of randomness, things we cannot quantify directly. Chance dogs our every shaving stroke.

Over the coming weeks and months I intend to discuss and (perhaps optimistically) explain in simple terms some of the common stochastic processes, probability distributions, and statistical techniques that might be applied to shaving. A lot of it will be theoretical in nature: I do not mean hardcore maths (though sometimes there might be maths); rather, I mean that I'll be discussing models. And models, as we all know, are just stylised versions of the real thing and are thus more often wrong than useful. However, it will at least keep me off the streets.

I'll leave you with a theorem and a thought. The theorem is known as Bayes' Theorem. Thomas Bayes, English cleric and part time mathematician (or vice-versa), lived and worked in the 1700's - interestingly, Bayes never published his work and the first formal definition to appear in the literature was published posthumously. In fact the French mathematician Laplace claimed to have rediscovered the theorem independently in the 19th century, thus continuing the well-worn path of European mathematicians claiming the work of their English betters as their own - see Liebnitz and Newton's calculus for an example that typifies the behaviour.... :). But I digress...

Bayes' theorem, at its core, is about conditional probability and how to swap that around. For example, suppose you have a drug test taken on an Italian cyclist and it has come up positive. The manufacturers of the drug test know certain things about the test through the copious amounts of trials they must undertake to have their test sanctioned by the governing body of cycling. Among the most important of these are the false positive rate (the probability that the test is positive, given the drug was not taken) and the false negative (the probability that the test is negative, given the drug was taken). These two rates are known as conditional probabilities: conditional on the fact we know one thing (eg that the drug was not taken), what is the probability of another thing happening (eg the test shows positive)? There are of course other conditional probabilities associated with these tests: true positive and true negative, for example.

In any event, the cylist's lawyer is only interested in one thing: Given the test is positive, what is the probability that the cyclist actually took the drug? If this probability is small enough, reasonable doubt can be applied and his client can go on to cheat his way to the top of another Tour De France in the future. :p If we denote D = taken drug and P = positive drug test, we can write the probability the lawyer is interested in as P(D | P). However, what we actually know is P(P | D), or the true positive rate. Bayes' theorem lets us reverse this conditioning via:

P(A|B) = [P(B|A)P(A)]/P(B)

so long as P(B) is not equal to zero (since dividing by zero is bad, M'kay?)

You will sometimes see Bayes' theorem written in its "proportional" form (without the P(B) in the denominator, and with the equals sign replaced with the "proportional to" sign, which looks like an infinity open at the right hand side):

P(A|B) \propto P(B|A) P(A)

The reason I have gone into (way, way too much) detail about this is that we can also use Bayes' theorem, particularly in the second (proportional) form, as a probabilistic or stochastic model for the way humans learn through experience. (Some people disagree with this statement, but they are wrong as this is my blog. They can get their own blog and sprout their misinformation on their own time.)

I will cover this idea in more detail in the next blog post, but for now suffice it to say that P(A) represents uncertainty about something interesting (A) prior to obtaining data (B) about it. P(A|B) is what we know (or our updated uncertainty) about A after seeing some data. P(B|A) quantifies how much information the data contains regarding A. So, for example:

P(Brush Loading | 50 shaves) \propto P(50 shaves | Brush Loading) P(Brush Loading)

or in words, what we know about loading our brush with soap after 50 shaves (P(BL|50)) is a combination of what we knew about brush loading before we did 50 shaves (P(B L) and how much information those 50 shaves gave us about brush loading (P(50|B L)).

Seems simple and intuitive, and it is. The best mathematical theorems always are.

Until next time,

James. ]]>

Call me Jimbo. Some time ago - never mind how long precisely - having little money in my purse, and nothing to interest me in the malls, I thought I would wander about in ebay and see a little of the straight razory part of the world. It is a way I have of driving off the ever-encroaching melancholia that seeps into my psyche, and of enhancing the circulation. Whenever I find myself growing grim around the chops, when it is a soggy ham sandwich in my soul, when the alarm clock in my heart has run out of batteries or the Windows of my life requires a control-alt-delete; when I find myself involuntarily raging at fellow motorists, or wishing I could give the fellow in front of me in the bank queue a wedgie, I account it high time to get myself to ebay. There is nothing surprising in this. If they but knew it, all men, to a greater or lesser degree, at some time or other, cherish within themselves very nearly the same yearning to view other people's varied and assorted crap as I.

Circumambulate the dreary byways of the interwebs on any night of the week. Go from Google to Yahoo, and from thence, by pop-up ad, toward compareprices.com. What do you see? - Perched like silent sentinels all around the site, man, woman, and child alike, a-hankerin' for a bargain. But these are all high street consumers; of weekdays trudging through sanitised, marbled, multi-storey car-parked, muzak-laden, escalator-driven, latte-fuelled shopping centres; chained to department stores; penned in and force-fed at the corporate trough. What do they here?

But look! Here comes more crowds, racing straight for the online auction, bound for a bargain. Nothing will content them but the most esoteric of miscellany. Loitering at the corporate website will not suffice! No! Nothing but wading deep into the detritus of mankind's abundant cast-offs will slake their lust.

Again. Say you are in the country, and require a hen-house. Wherefore to dost thou seek? Not the flashy chicken emporium on chicken lane! No, to ebay they flock, for a second-hand, pre-loved, as-new, never-been-used, from-non-smoking-household coop. Wary though they be in the ways of shipping costs, there is an inexorable draw to the web.

It is the glory of the chase, the thrill of the outmanoeuvre, the twitch of the finger, the guile of the snipe, the adrenaline and insanity of the bidding war, which draws man to the auction. It is the age-old image of man, standing tall and proud over a slain adversary, a triumphant chorus ringing in our ears, that holds the secret to our fascination with ebay.

Now, when I say I am in the habit of going a straight-razorin' on the ebay whenever I get a bit wild about the eyes, or twitchy around the nether regions, I do not mean it to be inferred that I go as a lurker. For to go as a lurker you must needs have your fill of razors and assorted accoutrements, and to have your fill of such things flies in the very face of all that a good straight razor man holds dear. No, I never go as a lurker. Nor do I ever go as a seller, nor a sniper. No, when I go to ebay, I go as a button-pushing, mouse-clicking, feverishly-page-refreshing buyer.

So what that I might, by some mistimed click, fail to refresh in time to beat the 5-second sniper? What is it to me that 5 days of patient waiting ends in some fool hitting the BIN button with 30 minutes to go? What consequence that the picture is blurry, or the seller has 80% positive feedback?

I go to ebay as a buyer for the chance to stumble across a rare and sought after thing; to proclaim my good fortune amongst other men; to hear the heartfelt acclaim and feel the hearty back-slaps; to see the envy in mine enemies eyes, and to hear the lamentation of their women!

By reason of these things then, an ebay voyage was welcome; the great flood-gates of the wonder-world swung open, and in the wild conceits that swayed me to my purpose, two and two there floated into my inmost soul, endless processions of the razor, and, mid most of them all, one grand hooded phantom, like a great silver frameback in the air. ]]>