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Drop data frame columns by name
...to keep and refer to them by name :
keeps <- c("y", "a")
DF[keeps]
EDIT :
For those still not acquainted with the drop argument of the indexing function, if you want to keep one column as a data frame, you do:
keeps <- "y"
DF[ , keeps, drop = FALSE]
drop=TRUE (or not mentioning it) will ...
Explain how finding cycle start node in cycle linked list work?
...
This is Floyd's algorithm for cycle detection. You are asking about the second phase of the algorithm -- once you've found a node that's part of a cycle, how does one find the start of the cycle?
In the first part of Floyd's algorithm, the hare...
PHP function to get the subdomain of a URL
...Or using your example:
array_shift((explode('.', 'en.example.com')));
EDIT: Fixed "only variables should be passed by reference" by adding double parenthesis.
EDIT 2: Starting from PHP 5.4 you can simply do:
explode('.', 'en.example.com')[0];
...
Download File to server from URL
Well, this one seems quite simple, and it is. All you have to do to download a file to your server is:
10 Answers
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Why does Vim save files with a ~ extension?
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The *.ext~ file is a backup file, containing the file as it was before you edited it.
The *.ext.swp file is the swap file, which serves as a lock file and contains the undo/redo history as well as any other internal info Vim needs. In case of a crash you can re-open your file and ...
Is it possible to change only the alpha of a rgba background colour on hover?
I have a set of <a> tags with differing rgba background colours but the same alpha. Is it possible to write a single css style that will change only the opacity of the rgba attribute?
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No 'Access-Control-Allow-Origin' - Node / Apache Port Issue
...venience):
// Add headers
app.use(function (req, res, next) {
// Website you wish to allow to connect
res.setHeader('Access-Control-Allow-Origin', 'http://localhost:8888');
// Request methods you wish to allow
res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT,...
Why do we need the “finally” clause in Python?
...
It makes a difference if you return early:
try:
run_code1()
except TypeError:
run_code2()
return None # The finally block is run before the method returns
finally:
other_code()
Compare to this:
try:
...
CGridCellNumeric - A numeric cell class for the MFC Grid - C/C++ - 清...
...ridCGridCellNumeric-A-numeric-cell-class-for-the-MFC-GridA locale aware, editable, self validating numeric cell class for the MFC Grid. Configurable for integers, floating...A locale aware, editable, self validating numeric cell class for the MFC Grid. Configurable for integers, floating point, or c...
Export to CSV via PHP
...-stream");
header("Content-Type: application/download");
// disposition / encoding on response body
header("Content-Disposition: attachment;filename={$filename}");
header("Content-Transfer-Encoding: binary");
}
Usage example:
download_send_headers("data_export_" . date("Y-m-d") ....