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What is the purpose of setting a key in data.table?
...e other vignettes that we plan to.
I've updated this answer again (Feb 2016) in light of the new on= feature that allows ad-hoc joins as well. See history for earlier (outdated) answers.
What exactly does setkey(DT, a, b) do?
It does two things:
reorders the rows of the data.table DT by the...
Can Visual Studio 2012 be installed side-by-side w/ Visual Studio 2010?
Will Visual Studio 2012 interfere/break .NET 4 and/or Visual Studio 2010 if installed side-by-side on the same instance of Windows?
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Allowed characters in Linux environment variable names
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206
From The Open Group:
These strings have the form
name=value; names shall not contain
th...
JavaScript equivalent of jQuery's extend method
... if(arguments[i].hasOwnProperty(key))
arguments[0][key] = arguments[i][key];
return arguments[0];
}
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PostgreSQL database default location on Linux
...:
[root@server1 ~]# ps auxw | grep postgres | grep -- -D
postgres 1535 0.0 0.1 39768 1584 ? S May17 0:23 /usr/local/pgsql/bin/postgres -D /usr/local/pgsql/data
Note that it is possible, though not very frequent, to run two instances of the same PostgreSQL server (same binaries, ...
make an html svg object also a clickable link
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answered Jul 7 '12 at 10:59
Erik DahlströmErik Dahlström
52.4k1111 gold badges106106 silver badges121121 bronze badges
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外部打开使用指导 · App Inventor 2 中文网
...的系统注册入口。
覆盖检查 7/7。首次载入及保存重开均0个错误，真实后台导入、安装包编译通过；真机／伴侣／硬件联调尚未实测。全部属性读写、方法与事件的操作入口和预期结果见组件指导。
安卓独立包链接唤起...
Removing double quotes from variables in batch file creates problems with CMD environment
...the following code to a batch file .cmd or .bat and run):
@ECHO OFF
ECHO %0
SET BathFileAndPath=%~0
ECHO %BathFileAndPath%
ECHO "%BathFileAndPath%"
ECHO %~0
ECHO %0
PAUSE
Output:
"C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd"
C:\Users\Test\Documents\Batch Files\Remove Quotes.cmd
"C:\Use...
Replacing all non-alphanumeric characters with empty strings
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250
Use [^A-Za-z0-9].
Note: removed the space since that is not typically considered alphanumeric....