Wikipedia:Reference desk/Archives/Computing/2015 July 14

= July 14 =

Do unread Facebook messages expire?
(Transferred from W:RDM due to recommendation) Despite having had a Facebook page for years, I have never once checked my messages. I didn't know I had them. So recently, when I found out, I wanted to read some old things just to see who and why people were writing someone who never went on Facebook. Well, I got one message from 2013 to load, but nothing older than that.

These messages are mostly from 2011, with a few from 2012. Are they not loading because of how long they've sat unread? --Ye Olde Luke (talk) 01:40, 14 July 2015 (UTC)


 * If they meant for them to expire, they would presumably have removed the link to them, too. I suspect that the server they were on was retired, or something like that, so that they have become inaccessible. StuRat (talk) 04:54, 14 July 2015 (UTC)
 * Are you by any chance guessing there, StuRat? --Viennese Waltz 08:33, 14 July 2015 (UTC)
 * You can read a bit about how FB Messenger works on the developer's blog. For efficiency reasons, the servers are structured so that the most recent messages are stored in a queue on a fast-access server (Facebook uses a variant of what's called the publish–subscribe pattern to send its messages, and Facebook has no way of knowing whether a user will read the next message on a phone or a computer, so they need to be ready for either contingency), while older messages are kept on traditional servers. I had a quick check, and although messages for 2010 and earlier take a few seconds to load, they do appear. Are you sure you have messages from that era? (Also, it's worth checking your "Other" inbox, which is where messages from groups and strangers are filed - I have some from before 2012 although when I try to load these I get errors, probably because of the way Groups, Pages and Messages work on Facebook have all changed over the last 4 years). Smurrayinchester 09:08, 14 July 2015 (UTC)

Sorting in Excel
As it will be quite hard to explain, what I want to do, I will show it with an example. So I have such table in Excel (this is just a small part of it)

And I want to get such result

As you can see, I want to get the same values in several columns for each row. In this case, the main column, by which I want to sort the data, is the first one and I want, that 3rd column sorts by the same values. -- Edgars2007  (talk/contribs) 09:10, 14 July 2015 (UTC)
 * VLOOKUP is your friend here. First, create a column containing all the possible index numbers, like this (I'm going to mark Excel cell references, to make this a bit clearer) So, here's your table. If the data isn't sorted, sort each pair of columns by the index (don't use the "Expand selection" operation when doing this sort) to close up empty rows and ensure everything is ordered:

Add a column ("E") containing a list of all possible index numbers

Now do VLOOKUP magic. VLOOKUP takes a number (or other string), finds that in the left-most column of an array you specify, and gives you the matching entry from that row of that array (to find entries, it needs the lookup values to be sorted). For this simple example, the VLOOKUP you want is:

The first variable ("E1" to "E5") is the cell whose value Excel will search for, the second ("$A$1:$B$5" or "$C$1:$D$5") is the array that Excel will search in (I've added the dollar signs to allow the formula to be auto-filled easily - if you've not come across this before, the Excel blog explains), the third variable ("2") is which column of the table contains the answer, and the fourth ("FALSE") tells Excel you want an exact match, not just a near-hit. This should resolve as:

If the #N/As are a problem, you can use an IFERROR function to hide them, like so:

This gives:


 * Hope this helps. Smurrayinchester 09:39, 14 July 2015 (UTC)
 * This looks very good. Thank you :) This will really save a lot of time. -- Edgars2007  (talk/contribs) 09:56, 14 July 2015 (UTC)

Ruler Add-on
Is there any add-on for Mozilla Firefox that I can use as a ruler, measuring distances on the screen in pixels, like you use the ‘Eyedropper’ to get the colour of a pixel? — Preceding unsigned comment added by Biolongvistul (talk • contribs) 13:10, 14 July 2015 (UTC)


 * Both "screen ruler" and "kruler" allow you to measure distance on the screen in pixels, but they are not Firefox add-ons. They are independent programs. 209.149.113.136 (talk) 13:54, 14 July 2015 (UTC)