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Grouping functions (tapply, by, aggregate) and the *apply family
...simple.
A vector:
x <- 1:20
A factor (of the same length!) defining groups:
y <- factor(rep(letters[1:5], each = 4))
Add up the values in x within each subgroup defined by y:
tapply(x, y, sum)
a b c d e
10 26 42 58 74
More complex examples can be handled where the subgroups...
Where do I set my company name?
...ies pane (at window
top-right, far right button in the
3-button "View" group).
In the "Project Document" section is
the "Organization" text field (File
Inspection view, second section from
top).
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Maximum length of the textual representation of an IPv6 address?
...ess to be
0000:0000:0000:0000:0000:0000:0000:0000
8 * 4 + 7 = 39
8 groups of 4 digits with 7 : between them.
But if you have an IPv4-mapped IPv6 address, the last two groups can be written in base 10 separated by ., eg. [::ffff:192.168.100.228]. Written out fully:
0000:0000:0000:0000:0000:...
Foreign keys in mongo?
...atabase like MongoDB there are not 'tables' but collections. Documents are grouped inside Collections. You can have any kind of document – with any kind of data – in a single collection. Basically, in a NoSQL database it is up to you to decide how to organise the data and its relations, if there...
How to open a web server port on EC2 instance
...e" an then "Add rule".
Go to the "Network & Security" -> Security Group settings in the left hand navigation
Find the Security Group that your instance is apart of
Click on Inbound Rules
Use the drop down and add HTTP (port 80)
Click Apply and enjoy
...
How to extract extension from filename string in Javascript? [duplicate]
... // undefined
Explanation
(?: # begin non-capturing group
\. # a dot
( # begin capturing group (captures the actual extension)
[^.]+ # anything except a dot, multiple times
) # end capturing group
)? # end non-capturing gro...
In SQL, what's the difference between count(column) and count(*)?
... to distinct values:
select column_a, count(distinct column_b)
from table
group by column_a
having count(distinct column_b) > 1;
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Merge multiple lines (two blocks) in Vim
...o know two things:
The line number on which the first line of the second group starts (5 in my case), and
the number of lines in each group (3 in my example).
Here's what's going on:
qa records everything up to the next q into a "buffer" in a.
ma creates a mark on the current line.
:5<CR>...
Fetch the row which has the Max value for a column
.....) OVER (...) you can also use ROW_NUMBER() OVER (...) (for the top-n-per-group) or RANK() OVER (...) (for the greatest-n-per-group).
– MT0
Jun 27 '16 at 8:13
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How can I parse a CSV string with JavaScript, which contains comma in data?
... # Allow whitespace before value.
(?: # Group for value alternatives.
'[^'\\]*(?:\\[\S\s][^'\\]*)*' # Either Single quoted string,
| "[^"\\]*(?:\\[\S\s][^"\\]*)*" # or Double quoted string,
| [^,'"\s\\]*(?:\s+[^,'"\s\\]+)* # or Non-comma, non-quote stu...