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dplyr summarise: Equivalent of “.drop=FALSE” to keep groups with zero length in output
...
Since dplyr 0.8 group_by gained the .drop argument that does just what you asked for:
df = data.frame(a=rep(1:3,4), b=rep(1:2,6))
df$b = factor(df$b, levels=1:3)
df %>%
group_by(b, .drop=FALSE) %>%
summarise(count_a=length(a)...
Showing the same file in both columns of a Sublime Text window
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edited Oct 22 '16 at 3:40
answered May 30 '14 at 23:33
Ma...
Validate that a string is a positive integer
...
302
Two answers for you:
Based on parsing
Regular expression
Note that in both cases, I've inte...
How assignment works with Python list slice?
...g two distinct operation that use very similar syntax:
1) slicing:
b = a[0:2]
This makes a copy of the slice of a and assigns it to b.
2) slice assignment:
a[0:2] = b
This replaces the slice of a with the contents of b.
Although the syntax is similar (I imagine by design!), these are two di...
Fastest hash for non-cryptographic uses?
...because of the reduced length (32 bits compared to 128 bits respectively 160 bits). But if you just want to check whether a stored string is corrupted, you'll be fine with CRC32.
share
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improve thi...
Python matplotlib multiple bars
...lotlib.dates import date2num
import datetime
x = [
datetime.datetime(2011, 1, 4, 0, 0),
datetime.datetime(2011, 1, 5, 0, 0),
datetime.datetime(2011, 1, 6, 0, 0)
]
x = date2num(x)
y = [4, 9, 2]
z = [1, 2, 3]
k = [11, 12, 13]
ax = plt.subplot(111)
ax.bar(x-0.2, y, width=0.2, color='b', ...
What is the most efficient/elegant way to parse a flat table into a tree?
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Now that MySQL 8.0 supports recursive queries, we can say that all popular SQL databases support recursive queries in standard syntax.
WITH RECURSIVE MyTree AS (
SELECT * FROM MyTable WHERE ParentId IS NULL
UNION ALL
SELECT m.* F...
What's the fastest way to loop through an array in JavaScript?
...yntactically obvious).
A standard for-loop with length caching
var i = 0, len = myArray.length;
while (i < len) {
// your code
i++
}
I would say, this is definitely a case where I applaud JavaScript engine developers. A runtime should be optimized for clarity, not cle...
Code Golf: Collatz Conjecture
Inspired by http://xkcd.com/710/ here is a code golf for it.
70 Answers
70
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