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How to iterate through two lists in parallel?
I have two iterables in Python, and I want to go over them in pairs:
8 Answers
8
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Replace all 0 values to NA
...ays in ?'NULL',
NULL represents the null object in R
which is unique and, I guess, can be seen as the most uninformative and empty object.1 Then it becomes not so surprising that
data.frame(x = c(1, NULL, 2))
# x
# 1 1
# 2 2
That is, R does not reserve any space for this null object.2 Mea...
Create an index on a huge MySQL production table without table locking
...ed to create an index on a ~5M rows MySQL table. It is a production table, and I fear a complete block of everything if I run a CREATE INDEX statement...
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Is R's apply family more than syntactic sugar?
...regarding execution time and / or memory.
5 Answers
5
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What is the Difference Between read() and recv() , and Between send() and write()?
What is the difference between read() and recv() , and between send() and write() in socket programming in terms of performances, speed and other behaviors?
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Resizing an image in an HTML5 canvas
I'm trying to create a thumbnail image on the client side using javascript and a canvas element, but when I shrink the image down, it looks terrible. It looks as if it was downsized in photoshop with the resampling set to 'Nearest Neighbor' instead of Bicubic. I know its possible to get this to lo...
What is a regular expression which will match a valid domain name without a subdomain?
...ote, to use this regex, you will need to convert the domain to lower case, and also use an IDN library to ensure you encode domain names to ACE (also known as "ASCII Compatible Encoding"). One good library is GNU-Libidn.
idn(1) is the command line interface to the internationalized domain name libr...
Why is SSE scalar sqrt(x) slower than rsqrt(x) * x?
I've been profiling some of our core math on an Intel Core Duo, and while looking at various approaches to square root I've noticed something odd: using the SSE scalar operations, it is faster to take a reciprocal square root and multiply it to get the sqrt, than it is to use the native sqrt opcode!...
How to validate an Email in PHP?
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You can use the filter_var() function, which gives you a lot of handy validation and sanitization options.
filter_var($email, FILTER_VALIDATE_EMAIL)
PHP Manual filter_var()
Available in PHP >= 5.2.0
If you don't want to change your code that relied on your function, just do:
func...
Do you use NULL or 0 (zero) for pointers in C++?
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Here's Stroustrup's take on this: C++ Style and Technique FAQ
In C++, the definition of NULL is 0, so there is only an aesthetic difference. I prefer to avoid macros, so I use 0. Another problem with NULL is that people sometimes mistakenly believe that it is differen...