Tiel schreef:LT schreef:Legendario schreef:LT schreef:Voorwaarts schreef:LT schreef:Hieruit blijkt veel, maar niet dat we veel meer kansen wisten te creëren. We hadden een ExpG van onder de 1, Heracles zat daar inclusief die penalty gewoon boven.
Niet helemaal eerlijk. De penalty alleen al was ongeveer 0.75 Als je die van de 1.15 afhaalt, blijft er slechts 0.40 over. Waar nec een totaal van 0.93 haalde. Dus ... meer dan het dubbele dus.
Dat is bij elkaar nog steeds niet eens een doelpunt hè.
Dan zijn we dus uiterst effectief in de afronding? Of hoe moet ik dat zien?
Afgelopen zondag wel, ja.
http://11tegen11.net/
De eerste regels verklaren genoeg, de hele mathematica erachter wil ik ook niet weten.
Dan geeft de werkelijk wedstrijd een compleet ander beeld dan de statistieken. Er wordt natuurlijk niet gekeken of het bv een grote of kleine schietkans is. MAW je hebt er niets aan. We waren zondag veel maar niet effectief.
Dan moet je toch echt even scrollen en even zoeken hoe ExpG wordt berekend. Dan had je deze opmerking namelijk niet gemaakt. Speciaal voor jou, om te laten weten dat het daadwerkelijk voldoet aan jouw verwachtingen:
Shot location
By far the most important predictor. Most models probably use shot zones, but I prefer a different method, which doesn’t have the granularity of zones, but rather uses location as a continuous parameter. In my model, location translates into two parameters: angle of view of the goal and distance from the goal.
Angle of view means two lines are drawn from the shot location to each post, and the angle between these lines signifies the view the player has. For very close shots, these angles go to a theoretical 180 degrees and for long range shots, or shots from acute angles, this approaches 0 degrees. Obviously, wide angles are better, since they signify closer shots from better angles.
Since the angle of view parameter is also in the model, the influence of distance on ExpG is a bit more complicated. Once angle is corrected for, distance has a positive impact. Think of a shot with an angle of view of just 5 degrees. This is either a close shot from a very acute angle, or a shot from way outside the box. The chance of scoring is higher for shots from outside the box than for shots from very acute angles, so more distance will raise ExpG in this particular model, where the angle of view is already corrected for.
Shot type
Foot shots are better than headers, after all other factors have been corrected for. However, a first attempt at implementing strong or weak foot did not improve the model. Perhaps we’ll get back at this one day.
Big Chance
Opta’s coders assign this code where they judge attempts to be big chances. This factor has quite a big impact on the ExpG, which supports the fact that on ball data alone is not enough to perfectly assess ExpG. Think of a weird long range shot when a keeper is out of place. For an ExpG model this will always be a hard attempt to qualify, since keeper position is not directly available. To me, this is a perfect example where data is helped by human judgement, since off ball event data would make analysis infinitely more complicated.
Start of possession
Attempts that result from possessions won high up the pitch have a higher chances of resulting in a goal than attempts from possession that started further down the pitch. A fine (but not the only) example where defensive pressure is in the ExpG model, though not directly but indirect. This factor is a recent addition, and based on some explorations there seems to be a sharp cut-off around 4/5th of the pitch. The difference is that sharp that for now I’ve put it in the model as a binary, either an attempt comes from a high turnover, or it doesn’t.
Assist
All attempts are either assisted or they are not. Assisted shots are assisted either intentionally or not. The unintentional assist stands for a casual pass that was never intended to provide a scoring chance, but was turned into a shot anyway. Opta makes this distinction, and I think it is very handy.
Intentional assists are a big plus for ExpG. This makes intuitive sense, since the assisting player makes a deliberate choice to allow a team mate to shoot (or head) the ball at goal, which illustrates a quality attempt.
Unintentional assists have a negative impact on ExpG compared to unassisted shots. Most of these attempts will be rather forced, and not of the highest quality. Unless, of course, a brilliant dribble precedes the attempt, but that kind of factors will come later.
Through ball
Nearly the best assist type possible. A through ball eliminates one or more defenders, forcing the remaining defenders into unwanted choices, and increasing the odds of scoring. Hence, a big bonus for ExpG.
One pass after a through ball
This is the best assist possible, as far as my variables go. It’s even better than a shot coming directly from a trough ball. Mostly this pass will be sideways to eliminate, or at least wrong-foot, the goal keeper.
Cross
Crosses are bad. This could be a title for a future post, but it is certainly true that crosses have an independent negative impact on ExpG. This is not to say teams should never cross a ball, or crossing as an offensive strategy is always bad, but it does say that after all other factors have been corrected for, crosses have quite a negative impact on ExpG. Crosses may be an efficient way to create goal scoring chances, but they won’t be the best way to create quality attempts. There is a balance in crosses somewhere. Too many signifies too low quality attempts and too few signifies a team that may create too few attempts.
Dribbles
Dribbles increase the odds of scoring. Much like a through ball, at least one defender is eliminated, but other than after a through ball, said defenders may come back into position later in the same attack. So, the effect is smaller than a through ball, but it does help. Oh, and more dribbles preceding the same attempt increase the effect, which makes intuitive sense.
Dribbles around the keeper
This is probably the biggest plus for ExpG. Shooting a football into an empty net is easier than scoring with the keeper in place, who’d have thought?
Vertical speed
Attacking at speed is beneficial in open play situations. This is measured quite roughly, since data is stamped by second, but it still has an independent effect on ExpG. Leaving defenders less time to settle is a good thing, and it can be measured.
Number of Touches
Creating attempts after lots of touches in a possession spell is good. It’s probably to be seen as a sign of dislocating the defense. This isn’t to say that the passing game is superior, but when it does result in an attempt, it seems to be a relatively good one.
Game State
Even after correcting for all factors above, Game State still has an independent effect on the odds of scoring. GS -1 is the hardest state to score. However, for direct free kicks this factor is not in place, which makes sense, as teams probably don’t defend direct free kicks differently according to the score line. This sounds better the other way around, teams do defend differently according to the score line in open play, but to a lesser extent also for indirect free kicks and corners. In regular play, the effect is much more pronounced for shots than for headers. Another case that makes sense, since those GS +1 counter attacks will be aimed at creating shots, rather than headers. Small note: since better teams lead more and poorer teams trail more, the debate about Game State is full of nuances and cannot fully be put to bed based on just this data.