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How to reorder data.table columns (without copying)
I'd like to reorder columns in my data.table x , given a character vector of column names, neworder :
2 Answers
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Sql Server equivalent of a COUNTIF aggregate function
I'm building a query with a GROUP BY clause that needs the ability to count records based only on a certain condition (e.g. count only records where a certain column value is equal to 1).
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List of all special characters that need to be escaped in a regex
I am trying to create an application that matches a message template with a message that a user is trying to send. I am using Java regex for matching the message. The template/message may contain special characters.
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scale Image in an UIButton to AspectFit?
I want to add an image to a UIButton, and also want to scale my image to fit with the UIButton (make image smaller). Please show me how to do it.
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JavaScript variable number of arguments to function
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Sure, just use the arguments object.
function foo() {
for (var i = 0; i < arguments.length; i++) {
console.log(arguments[i]);
}
}
share
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im...
Is there a Null OutputStream in Java?
I need to specify an OutputStream for an API I'm using, but I don't actually have a need for the output. Does Java have an OutputStream equivalent to > /dev/null ?
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URL encoding in Android
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You don't encode the entire URL, only parts of it that come from "unreliable sources".
String query = URLEncoder.encode("apples oranges", "utf-8");
String url = "http://stackoverflow.com/search?q=" + query;
Alternatively, you can use Strings.urlEncode(String str) of DroidParts that doesn't thro...
Why did my Git repo enter a detached HEAD state?
I ended up with a detached head today, the same problem as described in: git push says everything up-to-date even though I have local changes
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Regex not operator
...xt following (hence: lookahead) this doesn't (hence: negative) match this. But it doesn't actually consume the characters it matches (hence: zero-width).
There are actually 4 combinations of lookarounds with 2 axes:
lookbehind / lookahead : specifies if the characters before or after the point ar...
How to directly initialize a HashMap (in a literal way)?
...etonMap("key", "value").
For Java Version 9 or higher:
Yes, this is possible now. In Java 9 a couple of factory methods have been added that simplify the creation of maps :
// this works for up to 10 elements:
Map<String, String> test1 = Map.of(
"a", "b",
"c", "d"
);
// this works ...