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Convert column classes in data.table
I have a problem using data.table: How do I convert column classes? Here is a simple example: With data.frame I don't have a problem converting it, with data.table I just don't know how:
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How is null + true a string?
Since true is not a string type, how is null + true a string ?
7 Answers
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How to find the JVM version from a program?
I want to write a sample Java file in which I want to know the JVM version in which the class is running. Is there a way?
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Why are elementwise additions much faster in separate loops than in a combined loop?
Suppose a1 , b1 , c1 , and d1 point to heap memory and my numerical code has the following core loop.
10 Answers
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How are the points in CSS specificity calculated
Researching specificity I stumbled upon this blog - http://www.htmldog.com/guides/cssadvanced/specificity/
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count the frequency that a value occurs in a dataframe column
I have a dataset
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Why isn't vector a STL container?
Item 18 of Scott Meyers's book Effective STL: 50 Specific Ways to Improve Your Use of the Standard Template Library says to avoid vector <bool> as it's not an STL container and it doesn't really hold bool s.
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Sample random rows in dataframe
I am struggling to find the appropriate function that would return a specified number of rows picked up randomly without replacement from a data frame in R language? Can anyone help me out?
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Listing all permutations of a string/integer
A common task in programming interviews (not from my experience of interviews though) is to take a string or an integer and list every possible permutation.
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What does curly brackets in the `var { … } = …` statements do?
Not sure if this is a Mozilla-specific JS syntax, but I often found variables being declared this way, for example, in add-on SDK docs :
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