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How to reorder data.table columns (without copying)
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# [3,] 0.3297416 1 3
From ?setcolorder:
In data.table parlance, all set* functions change their input by reference. That is, no copy is made at all, other than temporary working memory, which is as large as one column.
so should be pretty efficient. See ?setcolorder for details.
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Generating a random & unique 8 character string using MySQL
... us to concentrate on the uniqueness first. Non-random uniqueness can trivially be achieved with AUTO_INCREMENT. So using a uniqueness-preserving, pseudo-random transformation would be fine:
Hash has been suggested by @paul
AES-encrypt fits also
But there is a nice one: RAND(N) itself!
A sequenc...
How does the Google “Did you mean?” Algorithm work?
...gement tool. There is a lot of text data, company names etc. I've been really impressed with some search engines ability to very quickly respond to queries with "Did you mean: xxxx".
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Avoiding instanceof in Java
...is entry from Steve Yegge's Amazon blog: "when polymorphism fails". Essentially he's addressing cases like this, when polymorphism causes more trouble than it solves.
The issue is that to use polymorphism you have to make the logic of "handle" part of each 'switching' class - i.e. Integer etc. in ...
What is so bad about singletons? [closed]
...haned by the developer world. I still use quite a lot of singletons, especially for factory classes , and while you have to be a bit careful about multithreading issues (like any class actually), I fail to see why they are so awful.
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Beautiful Soup and extracting a div and its contents by ID
... Well, then it's impossible to answer your question, crystal balls are not a reliable way of debugging. :)
– Lukáš Lalinský
Jan 25 '10 at 23:00
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Crontab - Run in directory
...t I would like it to execute it from a particular directory so it can find all the files it needs, since the application has a bunch of relative paths.
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How to “undelete” a deleted folder in Subversion / TortoiseSVN?
We have accidentally deleted the 'tags' folder from our Subversion repository where we only intended to delete one specific tag. What is the easiest way to get the 'tags' folder back?
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One line ftp server in python
...k and temporary way to transfer files to a linux box without having to install a ftp server. Preferably a way using built in python libraries so there's nothing extra to install.
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What is the benefit of using Fragments in Android, rather than Views?
...tom views are more light weight and simpler to implement.
At first, I actually tried to build a phone/tablet app using custom views. Everything appeared to work across phones AND tablets, even switching from single panel to split panel. Where I ran into trouble was with the back button and life c...