大约有 49,000 项符合查询结果（耗时：0.0380秒） [XML]
Repeat each row of data.frame the number of times specified in a column
...es
library(dplyr)
df %>%
slice(rep(seq_len(n()), freq)) %>%
select(-freq)
# var1 var2
#1 a d
#2 b e
#3 b e
#4 c f
#5 c f
#6 c f
seq_len(n()) part can be replaced with any of the following.
df %>% slice(rep(1:nrow(df), freq)) %>% select(-...
Can't install PIL after Mac OS X 10.9
...ution below, provided by Will.
open your terminal and execute:
xcode-select --install
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MySQL convert date string to Unix timestamp
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Here's an example of how to convert DATETIME to UNIX timestamp:
SELECT UNIX_TIMESTAMP(STR_TO_DATE('Apr 15 2012 12:00AM', '%M %d %Y %h:%i%p'))
Here's an example of how to change date format:
SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(STR_TO_DATE('Apr 15 2012 12:00AM', '%M %d %Y %h:%i%p')),'%m-%d-...
jQuery Selector: Id Ends With?
Is there a selector that I can query for elements with an ID that ends with a given string?
9 Answers
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C# - Selectively suppress custom Obsolete warnings
... },
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true,enableSnippets:true
});
}
});
...
'Java' is not recognized as an internal or external command
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For Windows 7:
Right click on My Computer
Select Properties
Select Advanced System Settings
Select Advanced tab
Select Environment Variables
Select Path under System Variables
Click on Edit button
In Variable value editor paste this at the start of the line
C:\Progr...
Can I bind an array to an IN() condition?
...(0, count($ids), '?'));
$db = new PDO(...);
$stmt = $db->prepare(
'SELECT *
FROM table
WHERE id IN(' . $inQuery . ')'
);
// bindvalue is 1-indexed, so $k+1
foreach ($ids as $k => $id)
$stmt->bindValue(($k+1), $id);
$stmt->execute();
?>
fix: dan, you were right. ...
Convert a list of objects to an array of one of the object's properties
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You are looking for
MyList.Select(x=>x.Name).ToArray();
Since Select is an Extension method make sure to add that namespace by adding a
using System.Linq
to your file - then it will show up with Intellisense.
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Use LINQ to get items in one List, that are not in another List
...erride the equality:
var excludedIDs = new HashSet<int>(peopleList1.Select(p => p.ID));
var result = peopleList2.Where(p => !excludedIDs.Contains(p.ID));
This variant does not remove duplicates.
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Count the occurrences of DISTINCT values
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SELECT name,COUNT(*) as count
FROM tablename
GROUP BY name
ORDER BY count DESC;
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