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What does .SD stand for in data.table in R
.SD looks useful but I do not really know what I am doing with it. What does it stand for? Why is there a preceding period (full stop). What is happening when I use it?
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Structs versus classes
...are "on the stack"). But they take longer to copy than a reference copy. I don't know what your performance metrics are for memory usage or speed; there's a tradeoff here and you're the person who knows what it is.
Is it better to create these objects as class or as struct?
Maybe class, maybe ...
What's the difference between %s and %d in Python string formatting?
I don't understand what %s and %d do and how they work.
12 Answers
12
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Identifying the dependency relationship for python packages installed with pip
When I do a pip freeze I see large number of Python packages that I didn't explicitly install, e.g.
8 Answers
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How to delete multiple values from a vector?
...ut I'd include it for the sake of readability.
This is, btw., what setdiff does internally (but without the unique to throw away duplicates in a which are not in remove).
If remove contains incomparables, you'll have to check for them individually, e.g.
if (any (is.na (remove)))
a <- a [! is....
Setting ANDROID_HOME enviromental variable on Mac OS X
...re the Android-SDK is installed depends on how you installed it.
If you downloaded the SDK through their website and then dragged/dropped the Application to your Applications folder, it's most likely here:
/Applications/ADT/sdk (as it is in your case).
If you installed the SDK using Homebrew (br...
Check OS version in Swift?
... While this is correct for objective c there is a much nicer way of doing it in swift. Outlined here... hackingwithswift.com/new-syntax-swift-2-availability-checking
– Fogmeister
Jul 6 '16 at 23:08
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How can I convert a datetime object to milliseconds since epoch (unix time) in Python?
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It appears to me that the simplest way to do this is
import datetime
epoch = datetime.datetime.utcfromtimestamp(0)
def unix_time_millis(dt):
return (dt - epoch).total_seconds() * 1000.0
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What is object slicing?
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@Felix Thanks but I don't think casting back (since not a pointer arithmetic) will work , A a = b; a is now object of type A which has copy of B::foo. It will be mistake to cast it back now i think.
– user72424
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What's the difference between equal?, eql?, ===, and ==?
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I'm going to heavily quote the Object documentation here, because I think it has some great explanations. I encourage you to read it, and also the documentation for these methods as they're overridden in other classes, like String.
Side note: if you want to try t...