大约有 45,300 项符合查询结果（耗时：0.0260秒） [XML]
git: Show index diff in commit message as comment
...
answered Jan 20 '11 at 17:09
Alan Haggai AlaviAlan Haggai Alavi
65.4k1818 gold badges9494 silver badges123123 bronze badges
...
Should I use a data.frame or a matrix?
...e the choice.
Also:
Matrices are more memory efficient:
m = matrix(1:4, 2, 2)
d = as.data.frame(m)
object.size(m)
# 216 bytes
object.size(d)
# 792 bytes
Matrices are a necessity if you plan to do any linear algebra-type of operations.
Data frames are more convenient if you frequently refer to ...
PostgreSQL - max number of parameters in “IN” clause?
...
Jordan S. JonesJordan S. Jones
12.6k44 gold badges3939 silver badges4949 bronze badges
add a ...
Ruby: What is the easiest way to remove the first element from an array?
...
291
"pop"ing the first element of an Array is called "shift" ("unshift"
being the operation of add...
Validate phone number with JavaScript
...ectly. It validates that the phone number is in one of these formats:
(123) 456-7890 or 123-456-7890
26 Answers
...
How to calculate “time ago” in Java?
...
|
edited Nov 28 '16 at 8:15
jdersen
21211 silver badge1313 bronze badges
answered Oct 4 '10...
Clojure: cons (seq) vs. conj (list)
...guments to insert into a collection, while cons takes just one:
(conj '(1 2 3) 4 5 6)
; => (6 5 4 1 2 3)
(cons 4 5 6 '(1 2 3))
; => IllegalArgumentException due to wrong arity
Another difference is in the class of the return value:
(class (conj '(1 2 3) 4))
; => clojure.lang.Persistent...
Which equals operator (== vs ===) should be used in JavaScript comparisons?
...
1
2
Next
6597
...
Time complexity of Sieve of Eratosthenes algorithm
...
Your n/2 + n/3 + n/5 + … n/97 is not O(n), because the number of terms is not constant. [Edit after your edit: O(n2) is too loose an upper bound.] A loose upper-bound is n(1+1/2+1/3+1/4+1/5+1/6+…1/n) (sum of reciprocals of all n...