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dplyr summarise: Equivalent of “.drop=FALSE” to keep groups with zero length in output
...b, .drop=FALSE) %>%
summarise(count_a=length(a))
#> # A tibble: 3 x 2
#> b count_a
#> <fct> <int>
#> 1 1 6
#> 2 2 6
#> 3 3 0
One additional note to go with @Moody_Mudskipper's answer: Using .drop=FALSE can give potentially...
Does Ruby regular expression have a not match operator like “!~” in Perl?
I just want to know whether ruby regex has a not match operator just like !~ in perl. I feel it's inconvenient to use (?!xxx) or (?<!xxxx) because you cannot use regex patterns in the xxx part.
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Why '&&' and not '&'?
...eaning that the evaluation is canceled as soon as the result is clear.
Example:
if(CanExecute() && CanSave())
{
}
If CanExecute returns false, the complete expression will be false, regardless of the return value of CanSave. Because of this, CanSave is not executed.
This is very handy...
Differences between contentType and dataType in jQuery ajax function
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From the documentation:
contentType (default: 'application/x-www-form-urlencoded; charset=UTF-8')
Type: String
When sending data to the server, use this content type. Default is "application/x-www-form-urlencoded; charset=UTF-8", which is fine for most cases. If you explicitly pass i...
Open terminal here in Mac OS finder [closed]
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As of Mac OS X Lion 10.7, Terminal includes exactly this functionality as a Service. As with most Services, these are disabled by default, so you'll need to enable this to make it appear in the Services menu.
System Preferences > K...
Validating IPv4 addresses with regexp
I've been trying to get an efficient regex for IPv4 validation, but without much luck. It seemed at one point I had had it with (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?(\.|$)){4} , but it produces some strange results:
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Send POST data using XMLHttpRequest
I'd like to send some data using an XMLHttpRequest in JavaScript.
13 Answers
13
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Will Dispose() be called in a using statement with a null object?
...using statement on a (potentially) null object?
Consider the following example:
5 Answers
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CSS force image resize and keep aspect ratio
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img {
display: block;
max-width:230px;
max-height:95px;
width: auto;
height: auto;
}
<p>This image is originally 400x400 pixels, but should get resized by the CSS:</p>
<img width="400" height="400" src="http://i.stack.imgu...
Batch files - number of command line arguments
...ing a bit gives you the following result from wikibooks:
set argC=0
for %%x in (%*) do Set /A argC+=1
echo %argC%
Seems like cmd.exe has evolved a bit from the old DOS days :)
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