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How to get subarray from array?
I have var ar = [1, 2, 3, 4, 5] and want some function getSubarray(array, fromIndex, toIndex) , that result of call getSubarray(ar, 1, 3) is new array [2, 3, 4] .
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What would cause an algorithm to have O(log n) complexity?
...ere are a few:
Repeatedly dividing by a constant
Take any number n; say, 16. How many times can you divide n by two before you get a number less than or equal to one? For 16, we have that
16 / 2 = 8
8 / 2 = 4
4 / 2 = 2
2 / 2 = 1
Notice that this ends up taking four steps to complete. Inte...
How to initialize an array in one step using Ruby?
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192
You can use an array literal:
array = [ '1', '2', '3' ]
You can also use a range:
array = ...
How to reorder data.table columns (without copying)
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185
Use setcolorder():
library(data.table)
x <- data.table(a = 1:3, b = 3:1, c = runif(3))
x
#...
Formatting Decimal places in R
I have a number, for example 1.128347132904321674821 that I would like to show as only two decimal places when output to screen (or written to a file). How does one do that?
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Single Line Nested For Loops
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172
The best source of information is the official Python tutorial on list comprehensions. List c...
App Inventor 2 数学代码块 · App Inventor 2 中文网
...最多的元素 (mode)
案例：指定将二进制的某一位(Bit)改为1
案例：指定将二进制的某一位(Bit)改为0
基础数字块 ( 0 )
进制数字块 ( 0 )
等于 ( = )
不等于 ( ≠ )
大于 ( > )
大于等于 ( ≥ )
小于 ( < )
小于等于 ( ≤ )
加 (...
How to add new item to hash
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Create the hash:
hash = {:item1 => 1}
Add a new item to it:
hash[:item2] = 2
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How to convert a data frame column to numeric type?
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SQL query return data from multiple tables
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Part 1 - Joins and Unions
This answer covers:
Part 1
Joining two or more tables using an inner join (See the wikipedia entry for additional info)
How to use a union query
Left and Right Outer Joins (this stackOverflow answer ...