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Subset of rows containing NA (missing) values in a chosen column of a data frame
We have a data frame from a CSV file. The data frame DF has columns that contain observed values and a column ( VaR2 ) that contains the date at which a measurement has been taken. If the date was not recorded, the CSV file contains the value NA , for missing data.
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Can I export a variable to the environment from a bash script without sourcing it?
Suppose that I have this script
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Intent - if activity is running, bring it to front, else start a new one (from notification)
My app has notifications, which - obviously - without any flags, start a new activity every time so I get multiple same activities running on top of each other, which is just wrong.
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Tree data structure in C#
I was looking for a tree or graph data structure in C# but I guess there isn't one provided. An Extensive Examination of Data Structures Using C# 2.0 explains a bit about why. Is there a convenient library which is commonly used to provide this functionality? Perhaps through a strategy pattern t...
Using the “final” modifier whenever applicable in Java [closed]
In Java, there is a practice of declaring every variable (local or class), parameter final if they really are.
25 Answers
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Is the pImpl idiom really used in practice?
I am reading the book "Exceptional C++" by Herb Sutter, and in that book I have learned about the pImpl idiom. Basically, the idea is to create a structure for the private objects of a class and dynamically allocate them to decrease the compilation time (and also hide the private implementatio...
Difference between reduce and foldLeft/fold in functional programming (particularly Scala and Scala
Why do Scala and frameworks like Spark and Scalding have both reduce and foldLeft ? So then what's the difference between reduce and fold ?
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How do SQL EXISTS statements work?
I'm trying to learn SQL and am having a hard time understanding EXISTS statements. I came across this quote about "exists" and don't understand something:
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How can I dynamically create a selector at runtime with Objective-C?
I know how to create a SEL at compile time using @selector(MyMethodName:) but what I want to do is create a selector dynamically from an NSString . Is this even possible?
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How do I wait for an asynchronously dispatched block to finish?
I am testing some code that does asynchronous processing using Grand Central Dispatch. The testing code looks like this:
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