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How important is the order of columns in indexes?
...while Column 1 above does negate 1/2 the possibilities, the index already knows which index page to go straight to for the Column2 value, it does not necessary need Column 1 to narrow down the set.
– CodeCowboyOrg
Mar 23 '15 at 17:57
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Can You Get A Users Local LAN IP Address Via JavaScript?
I know the initial reaction to this question is "no" and "it can't be done" and "you shouldn't need it, you are doing something wrong". What I'm trying to do is get the users LAN IP address, and display it on the web page. Why? Because that's what the page I'm working on is all about, showing as muc...
SPAN vs DIV (inline-block)
...pec, <span> is an inline element and <div> is a block element. Now that can be changed using the display CSS property but there is one issue: in terms of HTML validation, you can't put block elements inside inline elements so:
<p>...<div>foo</div>...</p>
is not...
if (key in object) or if(object.hasOwnProperty(key)
...someMap.constructor will yield -> function Object() { [native code] }
Now, if you want to iterate through "someMap" you will have to do it this way:
const key
for(key in someMap ){
if (someMap.hasOwnProperty(key)) {
// Do something
}
}
We are doing so in order to avoid iterating over i...
Parse large JSON file in Nodejs
...(pos == 0) { // if there's more than one newline in a row, the buffer will now start with a newline
buf = buf.slice(1); // discard it
continue; // so that the next iteration will start with data
}
processLine(buf.slice(0,pos)); // hand off the line
buf...
Calculate total seconds in PHP DateInterval
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Could you not compare the time stamps instead?
$now = new DateTime('now');
$diff = $date->getTimestamp() - $now->getTimestamp()
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How to configure postgresql for the first time?
...stgres:
local all postgres peer md5
To know what version of postgresql you are running, look for the version folder under /etc/postgresql. Also, you can use Nano or other editor instead of VIM.
Restart the database :
sudo /etc/init.d/postgresql restart
(Here ...
Save classifier to disk in scikit-learn
...digits.data, digits.target)
0.9526989426822482
Edit: in Python 3.8+ it's now possible to use pickle for efficient pickling of object with large numerical arrays as attributes if you use pickle protocol 5 (which is not the default).
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Fast stable sorting algorithm implementation in javascript
... stable sort.
I've written an article about it on my blog if you want to know more about this technique and how to implement it: http://blog.vjeux.com/2010/javascript/javascript-sorting-table.html
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What is an intuitive explanation of the Expectation Maximization technique? [closed]
...e could find the exact means if we wanted).
This is, generally speaking, known as maximum likelihood estimation. Given some data, we compute the value of a parameter (or parameters) that best explains that data.
Now imagine that we cannot see which value was sampled from which group. Everything lo...