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Group by multiple columns in dplyr, using string vector input
I'm trying to transfer my understanding of plyr into dplyr, but I can't figure out how to group by multiple columns.
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What is a postback?
I'm making my way into web development and have seen the word postback thrown around. Coming from a non-web based background, what does a new web developer have to know about postbacks? (i.e. what are they and when do they arise?)
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Get the name of an object's type
... return the name of the constructor as a string. I have tested this in FF3 and IE7, I can't speak for other implementations.
If you don't want to do that, here is a discussion on the various ways of determining types in JavaScript...
I recently updated this to be a bit more exhaustive, though it is...
Why use apparently meaningless do-while and if-else statements in macros?
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The do ... while and if ... else are there to make it so that a
semicolon after your macro always means the same thing. Let's say you
had something like your second macro.
#define BAR(X) f(x); g(x)
Now if you were to use BAR(X); in an if ...
Split string based on regex
...most regular expression operations are available as module-level functions and RegexObject methods. The functions are shortcuts that don’t require you to compile a regex object first, but miss some fine-tuning parameters." You can use re.split(re.split(pattern, string, maxsplit=0, flags=0)) as me...
Compile time string hashing
...ing's hash at compile time. However, no one seems to be ready to come out and say that it will be possible or how it would be done.
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Search of table names
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I'm using this and works fine
SELECT * FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME LIKE '%%'
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Check if a string contains a string in C++
...n';
}
Note: "found!" will be printed if s2 is a substring of s1, both s1 and s2 are of type std::string.
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Which iOS app version/build number(s) MUST be incremented upon App Store release?
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Apple Technical Note TN2420, Version Numbers and Build Numbers
Summary:
The pair (Version, Build number) must be unique.
The sequence is valid: (1.0.1, 12) -> (1.0.1, 13) -> (1.0.2, 13) -> (1.0.2, 14) ...
Version (CFBundleShortVersionString) must be in a...
Vim indent xml file
...want to format.
Then, in normal mode, type ! xmllint --format -
Your command-line at the bottom will look like this:
:'<,'>!xmllint --format -
Then hit enter.
Technical Explanation
The selected text is sent to the xmllint command, then --format'ed, and the results of xmllint are placed o...