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Determine the data types of a data frame's columns
I'm using R and have loaded data into a dataframe using read.csv() . How do I determine the data type of each column in the data frame?
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Checking to see if a DateTime variable has had a value assigned
...t; (or DateTime? with the C# syntactic sugar) - make it null to start with and then assign a normal DateTime value (which will be converted appropriately). Then you can just compare with null (or use the HasValue property) to see whether a "real" value has been set.
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curl : (1) Protocol https not supported or disabled in libcurl
...g to install the Rails environments on Ubuntu 11.04. When I launch the command rvm install 1.9.2 --with-openssl-dir=/usr/local the following error is received:
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How to install therubyracer gem on 10.10 Yosemite?
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It's also worth mentioning that if you're using a Gemfile and still having trouble installing therubyracer, it's probably because there's a different version of libv8 that's already been added to the Gemfile.lock. Just add gem 'libv8', '3.16.14.3' (or whatever is the exact version o...
Ruby: What is the easiest way to remove the first element from an array?
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Note this mutates the array and returns nil on an empty array. See drop for an alternative, as mentioned in the other answer.
– Jay
Oct 15 '15 at 21:37
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Convert string to a variable name
...ttp://www.r-bloggers.com/converting-a-string-to-a-variable-name-on-the-fly-and-vice-versa-in-r/
To convert a string to a variable:
x <- 42
eval(parse(text = "x"))
[1] 42
And the opposite:
x <- 42
deparse(substitute(x))
[1] "x"
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What's a reliable way to make an iOS app crash?
...ered Nov 22 '12 at 10:36
Daij-DjanDaij-Djan
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Writing files in Node.js
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I've tested this script using Node, and I tried changing the file path to "/home/", but I got the following error: { [Error: EACCES, open '/home/test.txt'] errno: 3, code: 'EACCES', path: '/home/test.txt' } How can I modify this script so that it will work out...
What is the best way to determine the number of days in a month with JavaScript?
...ve been using this function but I'd like to know what's the most efficient and accurate way to get it.
15 Answers
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Managing constructors with many parameters in Java
...e("Spicoli")
.age(16)
.motto("Aloha, Mr Hand")
.buildStudent();
If we leave off a required field (presumably name is required) then we can have the Student constructor throw an exception.
And it lets us have default/optional arguments without need...