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Group by multiple columns in dplyr, using string vector input
...e
df2 <- plyr::ddply(data, columns, plyr::summarize, value=mean(value))
table(df1 == df2, useNA = 'ifany')
## TRUE
## 27
The output from your example question is as expected (see comparison to plyr above and output below):
# A tibble: 9 x 3
# Groups: asihckhdoydkhxiydfgfTgdsx [?]
asihck...
Change cursor to hand when mouse goes over a row in table
...he cursor pointer to hand when my mouse goes over a <tr> in a <table>
11 Answers
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In Postgresql, force unique on combination of two columns
I would like to set up a table in PostgreSQL such that two columns together must be unique. There can be multiple values of either value, so long as there are not two that share both.
...
Is SHA-1 secure for password storage?
...ht now even with the "broken" hash functions MD5 and SHA-1.
About rainbow tables:
The "rainbow attack" is actually cost-sharing of a dictionary or brute force attack. It is a derivative from the time-memory trade-off first described by Hellman in 1980. Assuming that you have N possible passwords (...
How to do a FULL OUTER JOIN in MySQL?
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For a code SAMPLE transcribed from this SO question you have:
with two tables t1, t2:
SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
The query above works for special cases where a FULL OUTER JOIN operation would not produce any duplicat...
Code Golf: Lasers
...&redo}die/x/?true:false,$/
The first line loads the input into %t, a table of the board where $t{99*i+j} holds the character at row i,column j. Then,
%d=split//,'>.^1<2v3' ; ($r)=grep{$d|=$d{$t{$_}}}%t
it searches the elements of %t for a character that matches > ^ < or v, and s...
How to understand nil vs. empty vs. blank in Ruby
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I made this useful table with all the cases:
blank?, present? are provided by Rails.
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Reliable method to get machine's MAC address in C#
...d be many active connections on a machine and their order may not be predictable.
– Dave R.
Mar 9 '11 at 15:33
@DaveR....
Ways to save enums in database
...g.
But if you wanted to really do that, i would create a Suits dimension table:
| Suit | SuitID | Rank | Color |
|------------|--------------|---------------|--------|
| Unknown | 4 | 0 | NULL |
| Heart | 1 | 1 | Red ...
How to do a batch insert in MySQL
I have 1-many number of records that need to be entered into a table. What is the best way to do this in a query? Should I just make a loop and insert one record per iteration? Or is there a better way?
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