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Group by multiple columns in dplyr, using string vector input
...ike so:
data = data.frame(
asihckhdoydkhxiydfgfTgdsx = sample(LETTERS[1:3], 100, replace=TRUE),
a30mvxigxkghc5cdsvxvyv0ja = sample(LETTERS[1:3], 100, replace=TRUE),
value = rnorm(100)
)
# get the columns we want to average within
columns = names(data)[-3]
library(dplyr)
df1 <- data...
What's the difference between => , ()=>, and Unit=>
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def f(x: => Int) = x * x
If I call it like this
var y = 0
f { y += 1; y }
Then the code will execute like this
{ y += 1; y } * { y += 1; y }
Though that raises the point of what happens if there's a identifier name clash. In traditional call-by-name, a mechanism called capture-avoiding ...
Can I specify a custom location to “search for views” in ASP.NET MVC?
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10 Answers
10
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Sharing Test code in Maven
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190
I recommend using type instead of classifier (see also: classifier). It tells Maven a bit mor...
How to add an auto-incrementing primary key to an existing table, in PostgreSQL?
...mented)
Modern Versions of PostgreSQL
Suppose you have a table named test1, to which you want to add an auto-incrementing, primary-key id (surrogate) column. The following command should be sufficient in recent versions of PostgreSQL:
ALTER TABLE test1 ADD COLUMN id SERIAL PRIMARY KEY;
Older...
How to find out which view is focused?
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113
Call getCurrentFocus() on the Activity.
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How to use a variable inside a regular expression?
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10 Answers
10
Active
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Specifying column name in a “references” migration
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61
Do it manually:
add_column :post, :author_id, :integer
but now, when you create the belongs_t...
What is the “-->” operator in C++?
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edited Dec 23 '18 at 15:46
community wiki
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Modifying a subset of rows in a pandas dataframe
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edited Dec 3 '18 at 6:52
answered Sep 6 '12 at 19:37
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