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Subset of rows containing NA (missing) values in a chosen column of a data frame
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Never use =='NA' to test for missing values. Use is.na() instead. This should do it:
new_DF <- DF[rowSums(is.na(DF)) > 0,]
or in case you want to check a particular column, you can also use
new_DF <- DF[is.na(DF$Var),]
In case you...
What happens if I define a 0-size array in C/C++?
... C++ Builder 2009 also correctly gives an error: [BCC32 Error] test.c(3): E2021 Array must have at least one element
– Lundin
Mar 15 '12 at 15:43
1
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Angular ng-repeat Error “Duplicates in a repeater are not allowed.”
...art. It would be very, very easy to miss this issue during development and testing because your array never contained duplicates, only to have your app explode in production when it gets exposed to dupes for the first time. I've built Angular apps before without knowing about the "no dupes" restrict...
Java: What is the difference between and ?
...intln("In Static");
}
{
System.out.println("In Instance");
}
To test, use
Class<ByteCodeParent> bcp2 =(Class<ByteCodeParent>) Class.forName("ByteCodeParent");
ByteCodeParent bcp4= bcp2.newInstance();
...
How to click first link in list of items after upgrading to Capybara 2.0?
...gests:
https://thoughtbot.com/blog/write-reliable-asynchronous-integration-tests-with-capybara#find-the-first-matching-element
Bad:
first(".active").click
If there isn’t an .active element on the page yet, first will return nil and the click will fail.
Good:
If you want to make sure there's ex...
How can I check if a URL exists via PHP?
...simple example and will not match all the urls listed in there. See this test url: regex101.com/r/EpyDDc/2 If you want a better one, replace it with the one listed on your link ( mathiasbynens.be/demo/url-regex ) from diegoperini ; it seems to match all of them, see this testlink: regex101.com/r/...
Heroku/devise - Missing host to link to! Please provide :host parameter or set default_url_options[:
... this:
On Heroku, we run multiple Production environments for staging and testing, so we need a flexible solution for the production.rb environment file.
In production.rb
config.action_mailer.default_url_options = { :host => ENV['MAILER_URL'] }
Then set the MAILER_URL environment variable fo...
Async image loading from url inside a UITableView cell - image changes to wrong image while scrollin
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/* I have done it this way, and also tested it */
Step 1 = Register custom cell class (in case of prototype cell in table) or nib (in case of custom nib for custom cell) for table like this in viewDidLoad method:
[self.yourTableView registerClass:[CustomTableV...
How to make asynchronous HTTP requests in PHP
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In my testing, using exec("curl $url > /dev/null 2>&1 &"); is one of the fastest solutions here. It's immensely faster (1.9s for 100 iterations) than the post_without_wait() function (14.8s) in the "accepted" answer ...
Check if any ancestor has a class using jQuery
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I might venture to say (without testing this) that this method is better. Elem.parents will traverse the entire parent dom strucutre, where closest() should (probably) stop once it finds the nearest parent with that element and is therefore more efficient. ...