Why is it not always possible to compute the centroid of feature vectors?

Hi in the data mining and machine learning course that I’m taking there is a subject on feature spaces and there is this part about feature vector aggregation and metric spaces that I don’t really understand. Now our curriculum is basically a huge presentation and the whole information about feature vector aggregation fits on one slide, anyway what I don’t understand is this:

For a given sample $ D$ the centroid can be computed as $ C_D = \frac{1}{|D|}\cdot\sum_{o\in D} o$

and then it says: “In a general metric space (that is, not a vector space), where we only have pairwise distances, it might not be possible to compute a centroid”

I don’t really think I understand what “only pairwise distance” means (my guess is it has something to do with the fact that a metric space defines the distances between all pairs of elements in its set) or why the consequence of it is that you can’t always compute the centroid.

I read somewhere that metric spaces does not have to define addition or scaling and if that is the case it makes sense to me that you can not calculate the centroid. Is this what it essentially is about or am I completely misunderstanding something?

Ubuntu always hangs while installing in dual boot HP laptop

I recently bought an HP 14s laptop with Windows 10, and want to dual boot with Ubuntu (16 or 18). Ubuntu 16.04 did got install (with touchpad and WiFi driver issue, which I can still try to fix later on). But the main problem is that whenever I boot into Ubuntu, it works fine for a few seconds, and then suddenly hangs. There is no option left other than force shutdown. If instead, I try to replace it with Ubuntu 18.04, then it also starts hanging, and that too during the installation phase.

(UEFI mode here BTW)

I have tried everything that I can think of. Tried turning off the secure boot access, tried booting in Legacy mode instead, but nothing works.

Can anyone shed some light as to what could be causing such erratic behaviour and what could I do to fix this? Would be highly grateful as I look forward to installing Ubuntu on my new laptop.

FYI: Windows 10 works perfectly, without any problem at all.

Is a teleportation circle’s shimmering portal always open?

There is some disagreement regarding the status of a shimmering portal for a permanent teleportation circle.

My understanding is that the permanent circle has a permanently open shimmering portal.

The contesting opinion is that circle still requires a wizard to use a spell slot to open a portal in the circle.

To me their interpretation defeats the purpose of a permanent circle.

If a random squirrel discovered a permanent teleportation circle, would they see an open portal that they could enter?

On premises SP 2016 with Office Online Server always open doc in browser regardless of config

I’m working on SP 2016 Enterprise on premises with the April release of Office Online Server.

That all works and documents open in the browser.

Now I want to exclude a single document library from that behavior. The document library has a custom content type and document template that uses smart parts – these don’t work in Office Online Server.


  1. set the document library setting ‘Opening Documents in the Browser’ setting to ‘Open in client application’ – no effect

  2. activated the site collection feature ‘Open Documents in Client Application by Default’ – no effect

The clients are Windows 7, IE 11 and Office 2010. Chrome exhibits the same behavior – documents always open in Online Server.

Any ideas?

How do I have desktop always display favorites on left?

I use a TV thru HDMI and the adjustment for TV. It looks great. When I start in they AM there is usually the favorites bar on the left that displays my favorite programs. After a few times when the computer has gone into sleep mode (or whatever that is called) and I log back in, the bar on the left is gone and I have to hit “Activities” at the top for it to show up. I would like it to always be there. I went into “display” settings and the “Auto-hide the Dock” is off. That seems to be the only thing that sounds like it should apply.
Anyone know what to do?

Is asynchrony always necessary with microservices?

I’m reading about microservices and a consistent message I’m getting is that microservices should communicate via asynchronous means only. But I don’t see how this can work while also providing feedback to the user?

Taking an e-commerce application as an example, we may have an OrderService and a PaymentService. The client makes a request to the order service to complete the order, which in turn makes a request to the payment service to process the charge.

However, if the request to the payment service from the order service is asynchronous, how do we tell the user whether their order was successful, as the client is expecting a synchronous response from the order service?

Modular Abilities (Preparation Required) With Insubstantiality Probably Should Not Get a Savings For “Always On” or “Usually On”

Regarding insubstantiality, it seems to be switchable by default, because the core rules say:

Your “natural” form (physical or insubstantial) is considered a special effect. You must take this advantage if you can change between a physical and an insubstantial form.

I want to have characters with Modular Abilities with Preparation Required (1 hour). I want their standard list to include some version of Insubstantiality. The idea is that the party will take about an hour in the morning, at their base camp, to choose their powers for the day, and then they will have a sixteen-hour adventuring day, during which they probably won’t reconfigure their powers. If a player character goes insubstantial in the morning, I think the character can switch the insubstantiality on and off. However, if at some point the character wants to put a different power in the slot, that character will be out of the fight for a full hour while he/she gets reconfigured.

The basic cost would be 88 points for “can carry objects, no encumbrance” because I don’t want player characters running around naked. This would be a cost of (5+(3*88))*.5=135 for the basic switchable ability.

Insubstantiality can get a 50% cost savings for “always on.” If this could be turned off and turned back on instantly, this seems impermissible. Modular Abilities can always be turned off. However, if there is an hour-long delay, perhaps the savings is justified. The cost would seem to be (5+(3*44))*.5=69 character points.

In other words, I think you can get a 66-point savings if you are willing to take an hour-long delay before you can turn your power back on.

Question: Have I described the 69-point version correctly, or am I misunderstanding how it would work?

Update 1st row always of sharepoint list

I am using REST API to update in custom list of SharePoint Server. It is a dashboard and displays result as per logged in user. Is it possible to update 1st row always using REST API irrespective of ID of row? Rest API is updating table but I want to update 1st row always.


function UpdatePendingListItem(value)   {        $  .ajax       ({           url: _spPageContextInfo.webAbsoluteUrl + "/_api/web/lists/GetByTitle('<LIST_NAME>')/items(<ITEM_ID>)", // list item ID           type: "POST",           data: JSON.stringify           ({               __metadata:               {                   type: "SP.Data.<LIST_NAME>ListItem"               },              COLUMN_NAME1:value, COLUMN_NAME2: loginName          }),           headers:           {               "Accept": "application/json;odata=verbose",               "Content-Type": "application/json;odata=verbose",               "X-RequestDigest": $  ("#__REQUESTDIGEST").val(),               "IF-MATCH": "*",               "X-HTTP-Method": "MERGE"           },          async: false,           success: function(data, status, xhr)           {            },           error: function(xhr, status, error)           {            }       });  }  **code to call function and update:** getListItemsForView(_spPageContextInfo.webAbsoluteUrl,'<list_name>','<View_name>') .done(function(data) {      var items = data.d.results;     console.log("Waiting For Approval=" +data.d.results.length);      //for(var i = 0; i < items.length;i++) {        //  console.log(items[i].Title);      //}       if(DashboardItemCount==0) {       CreatePendingListItem(data.d.results.length); } else { UpdatePendingListItem(data.d.results.length); } }) .fail( function(error){     console.log(JSON.stringify(error)); }); 

Help improve player who always plays himself

In the group, where me and 3 of my friends play, one of my friend (lets call him John) always plays himself and always the same class, a swordfighter with psychic abilities.

John has been playing himself for 2 years, through 4 parties.

  • We have tried to convince him to change the class, to have a different atmosphere around his character. He said, that this is the only class that interests him.

  • We tried to have some roleplay practice night, where the GM assigned some predefined roles for a quick roleplay game. In one of these games, he had to play a fat butcher with some predefined traits: gullible, stupid and strong. He upright couldn’t play it, stating that he “thought of everything there is, but he is out of ideas”. We tried to encourage him with some ideas, but he rather not played it.

  • We tried to be forward with him and told him, that he plays himself, bringing up situations where he reacted the same, the way he talks (trying to sound “deep” and concerning), that he is always plays polite (except when woman NPC is around). But he denies it…

And its like he only like to focus on solving the quest, rather than playing the quest.

All of this wouldn’t be a problem, if his character would be fun, but it is not that case.

Any ideas how to help him accept that he plays himself, and help him be open about trying out other characters?

PS: It is a not well know rpg, only in my country