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Should I use the datetime or timestamp data type in MySQL?
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Timestamps in MySQL are generally used to track changes to records, and are often updated every time the record is changed. If you want to store a specific value you should use a datetime field.
If you meant that you want to decide between using a UNIX timestamp or a na...
How to sum a variable by group
...f you want to aggregate multiple columns, you could use the . notation (works for one column too)
aggregate(. ~ Category, x, sum)
or tapply:
tapply(x$Frequency, x$Category, FUN=sum)
First Second Third
30 5 34
Using this data:
x <- data.frame(Category=factor(c("First", ...
Getting the count of unique values in a column in bash
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To see a frequency count for column two (for example):
awk -F '\t' '{print $2}' * | sort | uniq -c | sort -nr
fileA.txt
z z a
a b c
w d e
fileB.txt
t r e
z d a
a g c
fileC.txt
z r a
v d c
a m c
Result:
3 d
2 r
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What is dynamic programming? [closed]
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Dynamic programming is when you use past knowledge to make solving a future problem easier.
A good example is solving the Fibonacci sequence for n=1,000,002.
This will be a very long process, but what if I give you the results for n=1,000,000 and n=1,000,001? Sudd...
Subqueries vs joins
...nherited from another company to use an inner join instead of a subquery like:
14 Answers
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How to break nested loops in JavaScript? [duplicate]
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You should be able to break to a label, like so:
function foo ()
{
dance:
for(var k = 0; k < 4; k++){
for(var m = 0; m < 4; m++){
if(m == 2){
break dance;
}
}
}
}
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How can I read command line parameters from an R script?
I've got a R script for which I'd like to be able to supply several command-line parameters (rather than hardcode parameter values in the code itself). The script runs on Windows.
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Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviations with _mm_popcnt_
I was looking for the fastest way to popcount large arrays of data. I encountered a very weird effect: Changing the loop variable from unsigned to uint64_t made the performance drop by 50% on my PC.
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CodeIgniter - accessing $config variable in view
Pretty often I need to access $config variables in views.
I know I can pass them from controller to load->view() .
But it seems excessive to do it explicitly.
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How to insert element into arrays at specific position?
...combine the parts.
$res = array_slice($array, 0, 3, true) +
array("my_key" => "my_value") +
array_slice($array, 3, count($array)-3, true);
This example:
$array = array(
'zero' => '0',
'one' => '1',
'two' => '2',
'three' => '3',
);
$res = array_slice($array, 0,...