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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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Can PNG image transparency be preserved when using PHP's GDlib imagecopyresampled?
...not the source image.
Edit:
full replacement code. See also answers below and their comments. This is not guaranteed to be be perfect in any way, but did achieve my needs at the time.
$uploadTempFile = $myField[ 'tmp_name' ]
list( $uploadWidth, $uploadHeight, $uploadType )
= getimagesize( $uplo...
List of lists changes reflected across sublists unexpectedly
...(3)]
which will reevaluate [1]*4 each time instead of evaluating it once and making 3 references to 1 list.
You might wonder why * can't make independent objects the way the list comprehension does. That's because the multiplication operator * operates on objects, without seeing expressions. Wh...
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...
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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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!...
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...
Do you use NULL or 0 (zero) for pointers in C++?
...
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...
What are Vertex Array Objects?
...://openglbook.com/the-book/
I got to chapter 2, where I draw a triangle, and I understand everything except VAOs (is this acronym OK?). The tutorial has this code:
...
Difference between DateTime and Time in Ruby
What's the difference between DateTime and Time classes in Ruby and what factors would cause me to choose one or the other?
...