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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 $2}' * | sort | uniq -c | sort -nr
fileA.txt
z z a
a b c
w d e
fileB.txt
t r e
z d a
a g c
fileC.txt
z r a
v d c
a m c
Result:
3 d
2 r
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Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviations with _mm_popcnt_
I was looking for the fastest way to popcount large arrays of data. I encountered a very weird effect: Changing the loop variable from unsigned to uint64_t made the performance drop by 50% on my PC.
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How to sum a variable by group
...f you want to aggregate multiple columns, you could use the . notation (works for one column too)
aggregate(. ~ Category, x, sum)
or tapply:
tapply(x$Frequency, x$Category, FUN=sum)
First Second Third
30 5 34
Using this data:
x <- data.frame(Category=factor(c("First", ...
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...
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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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,...
What is the difference between lower bound and tight bound?
... (it must be both the upper and lower bound).
For example, an algorithm taking Omega(n log n) takes at least n log n time, but has no upper limit. An algorithm taking Theta(n log n) is far preferential since it takes at least n log n (Omega n log n) and no more than n log n (Big O n log n).
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Subqueries vs joins
...nherited from another company to use an inner join instead of a subquery like:
14 Answers
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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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