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Why can't R's ifelse statements return vectors?
I've found R's ifelse statements to be pretty handy from time to time. For example:
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Remove all classes that begin with a certain string
I have a div with id="a" that may have any number of classes attached to it, from several groups. Each group has a specific prefix. In the javascript, I don't know which class from the group is on the div. I want to be able to clear all classes with a given prefix and then add a new one. If I want...
What is the difference between is_a and instanceof?
I am aware that instanceof is an operator and that is_a is a method.
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How to generate random SHA1 hash to use as ID in node.js?
I am using this line to generate a sha1 id for node.js:
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Removing multiple keys from a dictionary safely
I know how to remove an entry, 'key' from my dictionary d , safely. You do:
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Given an array of numbers, return array of products of all other numbers (no division)
I was asked this question in a job interview, and I'd like to know how others would solve it. I'm most comfortable with Java, but solutions in other languages are welcome.
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Why are arrays covariant but generics are invariant?
From Effective Java by Joshua Bloch,
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When someone writes a new programming language, what do they write it IN?
Please excuse my ignorance. I'm dabbling in PHP and getting my feet wet browsing SO, and feel compelled to ask a question that I've been wondering about for years:
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How to check if a map contains a key in Go?
I know I can iterate over a map m by,
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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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