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How to drop columns by name in a data frame
..."z","u"))]
x y
1 1 2
2 2 3
3 3 4
4 4 5
5 5 6
Or, much simpler, use the select argument of the subset function : you can then use the - operator directly on a vector of column names, and you can even omit the quotes around the names !
R> subset(df, select=-c(z,u))
x y
1 1 2
2 2 3
3 3 4
4 4 ...
TSQL - How to use GO inside of a BEGIN .. END block?
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@gbn @mellamokb: I meant statements like SELECT * <newline> FROM whatever. If I execute every line with its own EXEC statement, that will break. Or are you suggesting I break at every GO statement?
– BlueRaja - Danny Pflughoeft
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How to do a regular expression replace in MySQL?
...ositions and perform substring substitution and extraction, respectively.
SELECT REGEXP_REPLACE('Stackoverflow','[A-Zf]','-',1,0,'c');
-- Output:
-tackover-low
DBFiddle Demo
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SQL Server dynamic PIVOT query?
... @cols AS NVARCHAR(MAX),
@query AS NVARCHAR(MAX);
SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.category)
FROM temp c
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set @query = 'SELECT date, ' + @cols + ' from
(...
Convert a String In C++ To Upper Case
...like 30x worse than calling glibc's toupper in a loop.) There's a dynamic_cast of the locale that doesn't get hoisted out of the per-char loop. See my answer. On the plus side, this may be properly UTF-8 aware, but the slowdown doesn't come from handling UTF-8; it comes from using a dynamic_cast ...
tinyxml XML解析库下载（tinyxml2.h 和 tinyxml2.cpp） - 源码下载 - 清泛...
...InternedStr( const char* str ) {
Reset();
_start = const_cast<char*>(str);
}
void SetStr( const char* str, int flags=0 );
char* ParseText( char* in, const char* endTag, int strFlags );
char* ParseName( char* in );
private:
void Reset();
void Col...
What's the difference between IEquatable and just overriding Object.Equals()?
...it as much but the IEquatable<T> implementation does let you avoid a cast from System.Object which can make a difference if it's called frequently.
As noted on Jared Parson's blog though, you still must implement the Object overrides.
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JSON Array iteration in Android/Java
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You are using the same Cast object for every entry.
On each iteration you just changed the same object instead creating a new one.
This code should fix it:
JSONArray jCastArr = jObj.getJSONArray("abridged_cast");
ArrayList<Cast> castList= n...
Alternative to itoa() for converting integer to string C++? [duplicate]
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boost::lexical_cast works pretty well.
#include <boost/lexical_cast.hpp>
int main(int argc, char** argv) {
std::string foo = boost::lexical_cast<std::string>(argc);
}
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How do you specify a byte literal in Java?
...ered an integer (or long if followed by a "L"), so you must explicitly downcast it to a byte to pass it as a parameter. As far as I know there is no shortcut.
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