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How to convert a data frame column to numeric type?
... 3
4 d 4 4 d 4
5 e 5 5 e 5
and let us run:
> sapply(d, mode)
char fake_char fac char_fac num
"character" "character" "numeric" "numeric" "numeric"
> sapply(d, class)
char fake_char fac char...
Why is my program slow when looping over exactly 8192 elements?
...rom the program in question. The matrix img[][] has the size SIZE×SIZE, and is initialized at:
2 Answers
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Declaring variables inside or outside of a loop
...that str absolutely ought to be declared within the while loop. No ifs, no ands, no buts.
The only case where this rule might be violated is if for some reason it is of vital importance that every clock cycle must be squeezed out of the code, in which case you might want to consider instantiating s...
Does ruby have real multithreading?
...e confusing two very different things here: the
Ruby Programming Language and the specific threading model of one
specific implementation of the Ruby Programming Language. There
are currently around 11 different implementations of the Ruby
Programming Language, with very different and unique thr...
JavaScript checking for null vs. undefined and difference between == and ===
...hey're falsey:
if (!a) {
// `a` is falsey, which includes `undefined` and `null`
// (and `""`, and `0`, and `NaN`, and [of course] `false`)
}
This is defined by ToBoolean in the spec.
...and what is the difference between the null and undefined?
They're both values usually used to i...
How to get image height and width using java?
Is there any other way besides using ImageIO.read to get image height and width?
13 Answers
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Does Python support short-circuiting?
...
Yep, both and and or operators short-circuit -- see the docs.
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Type-juggling and (strict) greater/lesser-than comparisons in PHP
PHP is famous for its type-juggling. I must admit it puzzles me, and I'm having a hard time to find out basic logical/fundamental things in comparisons.
...
What are the Ruby Gotchas a newbie should be warned about? [closed]
I have recently learned the Ruby programming language, and all in all it is a good language. But I was quite surprised to see that it was not as simple as I had expected. More precisely, the "rule of least-surprise" did not seem very respected to me (of course this is quite subjective). For examp...
Unicode equivalents for \w and \b in Java regular expressions?
Many modern regex implementations interpret the \w character class shorthand as "any letter, digit, or connecting punctuation" (usually: underscore). That way, a regex like \w+ matches words like hello , élève , GOÄ_432 or gefräßig .
...