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How do you delete a column by name in data.table?
...the following will remove column foo from the data.table df3:
# Method 1 (and preferred as it takes 0.00s even on a 20GB data.table)
df3[,foo:=NULL]
df3[, c("foo","bar"):=NULL] # remove two columns
myVar = "foo"
df3[, (myVar):=NULL] # lookup myVar contents
# Method 2a -- A safe idiom for excl...
Code for Greatest Common Divisor in Python [closed]
The greatest common divisor (GCD) of a and b is the largest number that divides both of them with no remainder.
20 Answers
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Get content uri from file path in android
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thanks! second method works fine on 1.6, 2.1 and 2.2 but first one only on 2.2
– mishkin
Nov 30 '10 at 2:45
29
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How to detect if URL has changed after hash in JavaScript
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This, as I understand, works only for the change of the part after the # sign (hence the event name)? And not for full URL change, as seems to be implied by the question's title.
– NPC
May 27 '14 at 21:53...
Best practice multi language website
... before. Right now, I feel like it's time to get to know the possibilities and create my own personal preference to use in my upcoming projects.
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Why should I prefer to use member initialization lists?
... this case, the constructor for B will call the default constructor for A, and then initialize a.x to 3. A better way would be for B's constructor to directly call A's constructor in the initializer list:
B()
: a(3)
{
}
This would only call A's A(int) constructor and not its default constructo...
Python OpenCV2 (cv2) wrapper to get image size?
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cv2 uses numpy for manipulating images, so the proper and best way to get the size of an image is using numpy.shape. Assuming you are working with BGR images, here is an example:
>>> import numpy as np
>>> import cv2
>>> img = cv2.imread('foo.jpg')
&g...
Matching a space in regex
... space).
If you're looking for one or more, it's " *" (that's two spaces and an asterisk) or " +" (one space and a plus).
If you're looking for common spacing, use "[ X]" or "[ X][ X]*" or "[ X]+" where X is the physical tab character (and each is preceded by a single space in all those examples)...
How do I join two SQLite tables in my Android application?
I have an Android project that has a database with two tables: tbl_question and tbl_alternative .
4 Answers
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Get current URL with jQuery?
I am using jQuery. How do I get the path of the current URL and assign it to a variable?
32 Answers
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