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How to sum a variable by group
...e(cbind(x$Frequency, x$Metric2, x$Metric3) ...
(embedding @thelatemail comment), aggregate has a formula interface too
aggregate(Frequency ~ Category, x, sum)
Or if you want to aggregate multiple columns, you could use the . notation (works for one column too)
aggregate(. ~ Category, x, sum)...
Multiline strings in JSON
...at you think your are. Maybe this answer explains it better: stackoverflow.com/a/9295597/359996. Note especially the bit about double escaping.
– user359996
Mar 7 '14 at 17:28
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Are static variables shared between threads?
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There isn't anything special about static variables when it comes to visibility. If they are accessible any thread can get at them, so you're more likely to see concurrency problems because they're more exposed.
There is a visibility issue imposed by the JVM's memory model. Here's an ...
ERROR 2006 (HY000): MySQL server has gone away
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You should be able to put this on the command line, which will avoid temporarily editing a system file:<code>mysql --max_allowed_packet=1GM</code>
– Jan Steinman
Feb 13 '15 at 7:45
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Convert to/from DateTime and Time in Ruby
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Is it true that one should not use NSLog() on production code?
...p %@:(%d)> %@", self, [[NSString stringWithUTF8String:__FILE__] lastPathComponent], __LINE__, [NSString stringWithFormat:(s), ##__VA_ARGS__] )
#else
#define DebugLog( s, ... )
#endif
I found it easier to put this entire statement in the prefix header rather than its own file. You could, if...
PHP exec() vs system() vs passthru()
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They have slightly different purposes.
exec() is for calling a system command, and perhaps dealing with the output yourself.
system() is for executing a system command and immediately displaying the output - presumably text.
passthru() is for executing a system command which you wish the ra...
JUnit vs TestNG [closed]
... TestNG groups can be done in JUnit 4.8 with Categories: kentbeck.github.com/junit/doc/ReleaseNotes4.8.html.
– Kaitsu
Feb 1 '10 at 13:16
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jQuery pass more parameters into callback
...behavior differs a lot depending on JS runtime (read browser). Also try to compare the function name shown in stacktrace/breakpoint in Firebug.
– Ihor Kaharlichenko
May 25 '11 at 7:51
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How to initialize private static members in C++?
... is initialized: const integral types defined like this may be turned into compile time constants by the implementation. This isn't always what you want, since it ups the binary dependency: client code needs recompilation if the value changes.
– Steve Jessop
Oc...