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dplyr summarise: Equivalent of “.drop=FALSE” to keep groups with zero length in output
When using summarise with plyr 's ddply function, empty categories are dropped by default. You can change this behavior by adding .drop = FALSE . However, this doesn't work when using summarise with dplyr . Is there another way to keep empty categories in the result?
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Boolean operators && and ||
According to the R language definition , the difference between & and && (correspondingly | and || ) is that the former is vectorized while the latter is not.
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Difference between Pragma and Cache-Control headers?
I read about Pragma header on Wikipedia which says:
3 Answers
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Using -performSelector: vs. just calling the method
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Basically performSelector allows you to dynamically determine which selector to call a selector on the given object. In other words the selector need not be determined before runtime.
Thus even though these are equivalent:
[anObject aMethod];
[anObject p...
Is it bad practice to have a constructor function return a Promise?
I'm trying to create a constructor for a blogging platform and it has many async operations going on inside. These range from grabbing the posts from directories, parsing them, sending them through template engines, etc.
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Do you have to put Task.Run in a method to make it async?
I'm trying to understand async await in the simplest form. I want to create a very simple method that adds two numbers for the sake of this example, granted, it's no processing time at all, it's just a matter of formulating an example here.
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Difference between Grunt, NPM and Bower ( package.json vs bower.json )
I'm new to using npm and bower, building my first app in emberjs :).
I do have a bit of experience with rails, so I'm familiar with the idea of files for listing dependencies (such as bundler Gemfile)
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Why XML-Serializable class need a parameterless constructor
I'm writing code to do Xml serialization. With below function.
4 Answers
4
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What is the recommended approach towards multi-tenant databases in MongoDB?
I'm thinking of creating a multi-tenant app using MongoDB. I don't have any guesses in terms of how many tenants I'd have yet, but I would like to be able to scale into the thousands.
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What is the lifetime of a static variable in a C++ function?
If a variable is declared as static in a function's scope it is only initialized once and retains its value between function calls. What exactly is its lifetime? When do its constructor and destructor get called?
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