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1 hour ago, Droy was my hero said:

 

And some teams have it, some don't.
 

I think we're one of the sides that don't. 

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2 hours ago, Droy was my hero said:

IMO it isn't.  It is a simple tool for counting chances. It shouldn't be extrapolated from that to blame specific keepers, defenders or finishing.  And it certainly has its blind spots - some kinds of chances that get over rated or under rated.    xPts is probably pushing it a bit far too.

But as Marcotti points out, there is almost certainly something more than just creating chances in winning games.  For want of a better word I call it game management.
And some teams have it, some don't.
At the very least xG is a tool for highlighting that.

I was struck by Marcotti's mention of xG v Arsenal. He says it was 2.09 to 0.5, and yet the BBC gave it as 2.79 to 0.39. Either way, our expected goals were vastly greater than theirs, whether by a factor of 4 or a factor of 7, but why are different figures being quoted? It does highlight the subjectivity of deciding whether a chance should be converted. 

Statistically, a corner is equivalent to 0.02 goals*, but some teams are far better than others at takng and scoring from corners. Does xG change according to whether a corner is taken by a player who rarely gets it past the first defender or someone who is actually good at putting over crosses? Does xG change according to the keeper's percentage of shots to goals or whether the person to whom the chance falls is in good goal-scoring form?

*https://sports.stackexchange.com/questions/977/what-percent-of-corner-kicks-turn-into-goals

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44 minutes ago, Mark Kelly said:

I think we're one of the sides that don't. 

That indeed is what the xG table says.  And yes I get the same feeling watching us.
 

5 minutes ago, Backbiter said:

I was struck by Marcotti's mention of xG v Arsenal. He says it was 2.09 to 0.5, and yet the BBC gave it as 2.79 to 0.39. Either way, our expected goals were vastly greater than theirs, whether by a factor of 4 or a factor of 7, but why are different figures being quoted? It does highlight the subjectivity of deciding whether a chance should be converted. 

I have no idea where Sky or BBC get their xG from.
Creating an XG system is not simple.  It requires a lot of historical data.  From precise positions of the shot, to where the ball has been received from and many which are not talked about.
There are competing systems.  I look at understat because it is available free.  This at a minimum means that I can judge for myself whether it is working or not.  The outperformance of Liverpool and the underperformance of City and us is easy to believe.
A system is a black box in that it is pretty much impossible to explain how it calculates the xG of a given chance because the calculation is so complicated.
It is Machine learning, which means half the historical data will be given to the machine for it to generate a prediction model for xG (Training the model).  Then that model is used on the remaining data and its predictions compared to what actually happened to give an idea of how good the model is (Testing the model).

Then there is a lot of tweaking.  And this is why one company's model might differ from another's while be equally good overall.  Build the model, test it, tweak it, test it again.  Repeat many times.
I guess the data sources used are the same (presumable from Opta).

As an example of a tweak, One Data scientist might include the crowd size as a variable and find it has had some predictive power.  Another might say that crowd size is not a predictor even if there is some random correlation, and so choose to remove it from the data he analyses.  Generally the more kinds of data measurement you give the training model the better it appears to do on the training data.  But less kinds of data makes it perform better on the Test data.

 

28 minutes ago, Backbiter said:

Statistically, a corner is equivalent to 0.02 goals*, but some teams are far better than others at takng and scoring from corners. Does xG change according to whether a corner is taken by a player who rarely gets it past the first defender or someone who is actually good at putting over crosses? Does xG change according to the keeper's percentage of shots to goals or whether the person to whom the chance falls is in good goal-scoring form?

*https://sports.stackexchange.com/questions/977/what-percent-of-corner-kicks-turn-into-goals

Interesting - I have been searching for something like this for years, and am not surprised that your link is 8 years old.
It is a hard question to even define.  When is a goal scored from a corner?  With in 90 secs?  Only if the ball does not leave the box first?  Do short corners count?  

Quote

 

Understat:  
Our goal was to create the most precise method for shot quality evaluation.
For this case, we trained neural network prediction algorithms with the large dataset (>100,000 shots, over 10 parameters for each).

 

My working assumption is that xG is calculated based on the final shot, not the corner itself.  
But with rival modellers competing to get the best model, no one is going to tell you the details.

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Ham   

16 year old Harvey Elliott of Liverpool is a decent player and he's getting as lot of very positive press on Sky, BT and the BBC recently.

Can't help thinking that if he was a Chelsea player he's be " Harvey Elliott, famed for calling Harry Kane a mong on social media"

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Ham   

Not even football related but what are your thoughts on the Israel Folau debate?

Should a player have to compromise on his deep-rooted religious views for the sake of his sporting career?

I don't agree with his views per se but is it not bordering on mind control by the state to virtually ban alternative views?

 

 

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4 minutes ago, Ham said:

Should a player have to compromise on his deep-rooted religious views for the sake of his sporting career?

I don't think he said a word until he was 26, so he clearly managed to avoid controversy till then.
He seems to have become more vocal in last couple of years, and it mostly doesn't seem necessary.

There is a difference between having views and expressing views.  The compromise, if he chooses to accept it is only about what he expresses.  (And it isn't just religious people who have to be careful what they say on social media).

Having said that there are topics and topics.  Some of his anti-gay comments are well beyond where almost  all public opinion is today.  Whereas some of his anti-transgender comments are very much mainstream.  Hats off to Virginia Wade and Matina Navratilova for stating eloquently what most people think. 

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Ham   
17 minutes ago, Droy was my hero said:

I don't think he said a word until he was 26, so he clearly managed to avoid controversy till then.
He seems to have become more vocal in last couple of years, and it mostly doesn't seem necessary.

There is a difference between having views and expressing views.  The compromise, if he chooses to accept it is only about what he expresses.  (And it isn't just religious people who have to be careful what they say on social media).

Having said that there are topics and topics.  Some of his anti-gay comments are well beyond where almost  all public opinion is today.  Whereas some of his anti-transgender comments are very much mainstream.  Hats off to Virginia Wade and Matina Navratilova for stating eloquently what most people think. 

 

Looks like he was initially forced to declare his personal view (Wikipedia);

In 2017, the Turnbull government called a national postal survey on the question of changing Australian law to recognise same-sex marriage. In September, the ARU management declared the Wallabies in support of the change, prompting Folau to announce his personal opposition a day later on Twitter, where he wrote: "I love and respect all people for who they are and their opinions. but personally, I will not support gay marriage."[77][78] Folau later wrote in Players Voice: "I didn't agree with Bill Pulver taking a stance on the same sex marriage vote on behalf of the whole organisation, but I understand the reasons behind why he did."[69]

 

 

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chara   
33 minutes ago, Ham said:

Not even football related but what are your thoughts on the Israel Folau debate?

Should a player have to compromise on his deep-rooted religious views for the sake of his sporting career?

I don't agree with his views per se but is it not bordering on mind control by the state to virtually ban alternative views?

 

 

Such a slippery slope....the "I may not agree but defend the right to say it" issue......as you say Ham....is it bordering on mind control etc?....in sensible company most understand the limits of voicing opinions. What happens is that the limits get decreased and if someone disagrees with a viewpoint they can call for a ban on the subject. Again sensible voices understand boundaries as long as they are self applied not mandated by an agenda based body.

The subject in this case is the issue....but if views are not expressed it becomes a mind control or rather opinion control issue.

I do not know the answer and do not agree with his views BUT for example sometimes I disagree with your views and Droy's but would never ever call for silence from either of you..and many times I am in complete agreement with both of you..and then you both "squabble" as is your absolute right..both of you....and I applaud free speech...

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chara   
32 minutes ago, Droy was my hero said:

I don't think he said a word until he was 26, so he clearly managed to avoid controversy till then.
He seems to have become more vocal in last couple of years, and it mostly doesn't seem necessary.

There is a difference between having views and expressing views.  The compromise, if he chooses to accept it is only about what he expresses.  (And it isn't just religious people who have to be careful what they say on social media).

Having said that there are topics and topics.  Some of his anti-gay comments are well beyond where almost  all public opinion is today.  Whereas some of his anti-transgender comments are very much mainstream.  Hats off to Virginia Wade and Matina Navratilova for stating eloquently what most people think. 

See reply to Ham's post.....I wonder if his avoiding controversy was less avoiding than media focus changing?.....whilst we all said foolish stuff when young by 26 most of our views were formed and maturity gives us a chance to modify thoughts and opinions..except about our Chelsea opinions!!

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7 minutes ago, Ham said:

Looks like he was initially forced to declare his personal view (Wikipedia);

Yes.  I presume a postal survey is like a non-binding referendum, which pretty much implies that both sides are reasonable positions to take.
What was wrong was the ARU taking a team view.  I'd agree he was right to make his point there.
But it is one thing to declare a view on gay marriage, another to talk about sinners and going to hell.

1 minute ago, chara said:

Such a slippery slope....the "I may not agree but defend the right to say it" issue.

I think it is quite reasonable to pay sportsmen a lot of money while demanding contractually that they avoid controversial topics.
I don't think sportsmen have the right to say what they think.  

So on gays being sinners, he is miles away from modern standards and should shut up.
On gay marriage both views were common, and once the ARU comes up with the team view he has a right to disassociate himself.
On transgender, although a liberal elite might wish to claim he is being controversial, he is actually expressing very middle ground opinions (at least by UK standards).  But perhaps he should just shut up.
 

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