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Access multiple elements of list knowing their index
...I would like to create a new list, which contains element with index 1, 2, 5, from given list [-2, 1, 5, 3, 8, 5, 6]. What I did is:
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How to add multiple files to Git at the same time
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daxdax
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How to get first N elements of a list in C#?
...query a bus schedule in my project, so that at any time I can get the next 5 bus arrival times. How can I limit my query to the first 5 results?
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Assign multiple columns using := in data.table, by group
...1 hi hello
# 2: 2 2 hi hello
# 3: 3 3 hi hello
# 4: 1 4 hi hello
# 5: 2 5 hi hello
# 6: 3 6 hi hello
x[ , c("mean", "sum") := list(mean(b), sum(b)), by = a][]
# a b col1 col2 mean sum
# 1: 1 1 hi hello 2.5 5
# 2: 2 2 hi hello 3.5 7
# 3: 3 3 hi hello 4.5 9
# 4: 1 4 h...
Evaluate expression given as a string
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The eval() function evaluates an expression, but "5+5" is a string, not an expression. Use parse() with text=<string> to change the string into an expression:
> eval(parse(text="5+5"))
[1] 10
> class("5+5")
[1] "character"
> class(parse(text="5+5"))
[1] "expr...
Why does [5,6,8,7][1,2] = 8 in JavaScript?
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[1,2,3,4,5,6][1,2,3];
^ ^
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array + — array subscript access operation,
where index is `1,2,3`,
which is an expression that evaluates to `3`.
The seco...
regex for zip-code
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^\d{5}(?:[-\s]\d{4})?$
^ = Start of the string.
\d{5} = Match 5 digits (for condition 1, 2, 3)
(?:…) = Grouping
[-\s] = Match a space (for condition 3) or a hyphen (for condition 2)
\d{4} = Match 4 digits (for condition 2, 3...
How to select .NET 4.5.2 as a target framework in Visual Studio
I have installed .NET Framework 4.5.2 on Windows 8.1. But in Visual Studio 2013 I do not see the .NET Framework 4.5.2 option (see screenshot). How do I target my project for .NET 4.5.2?
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How to slice an array in Bash
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edited Jul 24 '18 at 16:35
Nicholas Pipitone
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ans...
Applying a function to every row of a table using dplyr?
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alexwhanalexwhan
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