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How to sort a dataframe by multiple column(s)
I want to sort a data.frame by multiple columns. For example, with the data.frame below I would like to sort by column z (descending) then by column b (ascending):
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Why are preprocessor macros evil and what are the alternatives?
...ved a really good answer; I think that almost any programmer before even writing the first "Hello World" had encountered a phrase like "macro should never be used", "macro are evil" and so on, my question is: why? With the new C++11 is there a real alternative after so many years?
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to drawRect or not to drawRect (when should one use drawRect/Core Graphics vs subviews/images and wh
...rify the purpose of this question: I know HOW to create complicated views with both subviews and using drawRect. I'm trying to fully understand the when's and why's to use one over the other.
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Difference between timestamps with/without time zone in PostgreSQL
... timestamp values stored differently in PostgreSQL when the data type is WITH TIME ZONE versus WITHOUT TIME ZONE ? Can the differences be illustrated with simple test cases?
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public friend swap member function
...ful answer to the copy-and-swap-idiom there is a piece of code I need a bit of help:
2 Answers
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How can I do string interpolation in JavaScript?
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Since ES6, you can use template literals:
const age = 3
console.log(`I'm ${age} years old!`)
P.S. Note the use of backticks: ``.
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Why is a boolean 1 byte and not 1 bit of size?
...tually, the four x86 instructions bt, bts, btr and btc can address single bits!
– fredoverflow
Jan 7 '11 at 16:07
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Unique (non-repeating) random numbers in O(1)?
...t doesn't resort to something like an O(N) search of previous values to do it. Is this possible?
22 Answers
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Python unittest - opposite of assertRaises?
I want to write a test to establish that an Exception is not raised in a given circumstance.
10 Answers
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ReactJS - Does render get called any time “setState” is called?
...te(object nextProps, object nextState), each component has this method and it's responsible to determine "should component update (run render function)?" every time you change state or pass new props from parent component.
You can write your own implementation of shouldComponentUpdate method for yo...