www.giannistsakiris.com

Since the day I started using Ubuntu as my every day (and night) OS, I noticed that for some reason the calendar was not showing up when I clicked on the clock applet. Later I discovered that the calendar was actually opened but hidden behind other windows.

It does the same in all (five) ubuntu desktops I have set up and have access to, so I believe it must be a bug of the Clock applet or something, so it will be fixed soon I think.

Until then, a workaround you may try is to click on any other open window, and the calendar will show up! But make sure you click on an application window. It will not work if you on the Desktop or the Panel.

This is a still image from a video I recorded last week on a rainy afternoon from my balcony. There was lots of lightnings in the sky and I thought it would be nice to take some shots of them, and this is what I finally came up with... I know, it's not a quite impressive one, but as soon I as have a better one I'll let you see! Winter is on his way...

Some websites allow their visitors to rank the articles or pictures they view, by voting a certain score, for example 1 for "bad" and up to 5 for "excellent". Then someone can request to view the top-rated items, with the ones with the highest score coming first.

The simpler way to implement this should be to have two fields for each item: number_of_votes and total_score. When a user votes for an item with a given score, you increase number_of_votes by one, and you add the selected score to total_score. Then you could just sort the items by the average scoring (total_score divided by number_of_votes) to get the top-rated ones. In terms of SQL that would be something like:

SELECT * FROM Items
ORDER BY total_score / number_of_votes DESC

This seems pretty much right, but it may lead into unwanted results. For example, assume two items A and B. Let's say item A has been voted 10 times, with a total score of 40. And item B has been voted only once given a score of 5. If we sort them with the method above, item B will come before item A because item B's average (5) is greater than item A's one (4).

Someone could argue about the validity of these results, claiming that item A with average score 4 should come first because this 4 was formed by a much larger number of opinions than a single one who believed that item B deserves a 5. Also, what would have happened if a third item, let's call it "C", was never voted yet? The aforementioned query would bring this item last, because a division by zero would return NULL. Or an implementer could even decide not to display items with zero votes at all. But is item C really worse than items A and B to deserve to be placed in the last position (or no position at all) in the results? Actually, we don't know.

A workaround to this problem would be to set a minimum number of votes required to consider an item's rating as valid. Until this minimum number of votes is reached, the item will be rated with the mean of the two extremes of the scores range (in our case that mean would be (5+1)/2=3). If we (arbitrarily) choose the minimum number of votes required to be 5, the query would be rewritten as follows (in the MySQL dialect):

SELECT * FROM Items
ORDER BY IF( number_of_votes >= 5,
total_score / number_of_votes, 3 ) DESC

A more precise approach would be to pad fake votes that give the item a score of the mean value, until the minimum number of votes is reached. In that case the query could be written as follows:

SELECT * FROM Items
ORDER BY IF( number_of_votes >= 5,
total_score / number_of_votes,
(total_score + 3*(5-number_of_votes) ) / 5 ) DESC

I did some tests and these seem to work pretty neat. However, I would really like to hear other people's opinions on this.

To change the default application for a file type in Ubuntu:

• Right click on the file for which you want to change the default application that opens it.


• Go to Properties and then open the Open With tab.


• From the list, select the application that you want to use as default using the radio buttons.

If the desired application is not listed click on the Add button to add it.

Note that the changes affect all the files of the same type.