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Remove an entire column from a data.frame in R
...on't need drop argument cause it always return data.frame from data.frame. And I think this is much better way to localized columns (and only columns) in data.frame (and it's faster). Check: cars[-1] (one col data.frame) or better cars[-(1:2)]: data frame with 0 columns and 50 rows.
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What's so wrong about using GC.Collect()?
Although I do understand the serious implications of playing with this function (or at least that's what I think), I fail to see why it's becoming one of these things that respectable programmers wouldn't ever use, even those who don't even know what it is for.
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Why historically do people use 255 not 256 for database field magnitudes?
...ric reason why? I assume it's something to do with paging / memory limits, and performance but the distinction between 255 and 256 has always confused me.
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How can I generate a list or array of sequential integers in Java?
Is there a short and sweet way to generate a List<Integer> , or perhaps an Integer[] or int[] , with sequential values from some start value to an end value?
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Initializing a struct to 0
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The first is easiest(involves less typing), and it is guaranteed to work, all members will be set to 0[Ref 1].
The second is more readable.
The choice depends on user preference or the one which your coding standard mandates.
[Ref 1] Reference C99 Standard 6.7.8...
Best way to select random rows PostgreSQL
I want a random selection of rows in PostgreSQL, I tried this:
12 Answers
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Split value from one field to two
I've got a table field membername which contains both the last name and the first name of users. Is it possible to split those into 2 fields memberfirst , memberlast ?
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What's a concise way to check that environment variables are set in a Unix shell script?
...(an empty string) is OK — not exactly what you want, but the alternative and older notation.
The second variant (using :?) requires DEST to be set and non-empty.
If you supply no message, the shell provides a default message.
The ${var?} construct is portable back to Version 7 UNIX and the Bourne ...
Remove rows with all or some NAs (missing values) in data.frame
... 1 2 3 2
but using complete.cases is quite a lot more clear, and faster.
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Why Choose Struct Over Class?
...n many circumstances.
Structs are preferable if they are relatively small and copiable because copying is way safer than having multiple references to the same instance as happens with classes. This is especially important when passing around a variable to many classes and/or in a multithreaded env...