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Flatten an Array of Arrays in Swift
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Swift >= 3.0
reduce:
let numbers = [[1,2,3],[4],[5,6,7,8,9]]
let reduced = numbers.reduce([], +)
flatMap:
let numbers = [[1,2,3],[4],[5,6,7,8,9]]
let flattened = numbers.flatMap { $0 }
joined:
let numbers = [[1,2,3],[4],[5,6,7,8,9]]
let joined = Array(number...
Operation on every pair of element in a list
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233
Check out product() in the itertools module. It does exactly what you describe.
import itert...
Numpy index slice without losing dimension information
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edited Nov 23 '17 at 5:53
Atcold
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answ...
Select multiple columns in data.table by their numeric indices
...llowing all just work:
library(data.table)
dt <- data.table(a = 1, b = 2, c = 3)
# select single column by index
dt[, 2]
# b
# 1: 2
# select multiple columns by index
dt[, 2:3]
# b c
# 1: 2 3
# select single column by name
dt[, "a"]
# a
# 1: 1
# select multiple columns by name
dt[, ...
Ruby max integer
... big they can be.
If you are looking for the machine's size, i.e. 64- or 32-bit, I found this trick at ruby-forum.com:
machine_bytes = ['foo'].pack('p').size
machine_bits = machine_bytes * 8
machine_max_signed = 2**(machine_bits-1) - 1
machine_max_unsigned = 2**machine_bits - 1
If you are look...
Get operating system info
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202
The code below could explain in its own right, how http://thismachine.info/ is able to show wh...
Best way to find the intersection of multiple sets?
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From Python version 2.6 on you can use multiple arguments to set.intersection(), like
u = set.intersection(s1, s2, s3)
If the sets are in a list, this translates to:
u = set.intersection(*setlist)
where *a_list is list expansion
Note that...
Memoization in Haskell?
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259
We can do this very efficiently by making a structure that we can index in sub-linear time.
B...
Running a cron job at 2:30 AM everyday
How to configure a cron job to run every night at 2:30? I know how to make it run at 2, but not 2:30.
6 Answers
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How to get row from R data.frame
...is, for example:
#Add your data
x <- structure(list(A = c(5, 3.5, 3.25, 4.25, 1.5 ),
B = c(4.25, 4, 4, 4.5, 4.5 ),
C = c(4.5, 2.5, 4, 2.25, 3 )
),
.Names = c("A", "B", "C"),
class = "da...