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Dynamically select data frame columns using $ and a character value
...itten as
`$`(df , V1)
or indeed
`$`(df , "V1")
But...
`$`(df , paste0("V1") )
...for instance will never work, nor will anything else that must first be evaluated in the second argument. You may only pass a string which is never evaluated.
Instead use [ (or [[ if you want to extract only...
Find XOR of all numbers in a given range
...ven a large range [a,b] where 'a' and 'b' can be typically between 1 and 4,000,000,000 inclusive. You have to find out the XOR of all the numbers in the given range.
...
Sample random rows in dataframe
...
460
First make some data:
> df = data.frame(matrix(rnorm(20), nrow=10))
> df
X1 ...
Is this a “good enough” random algorithm; why isn't it used if it's faster?
... QuickRandom qr = new QuickRandom();
int[] frequencies = new int[10];
for (int i = 0; i < 100000; i++) {
frequencies[(int) (qr.random() * 10)]++;
}
printDistribution("QR", frequencies);
frequencies = new int[10];
for (int i = 0; i <...
Use ffmpeg to add text subtitles [closed]
...
202
ffmpeg -i infile.mp4 -i infile.srt -c copy -c:s mov_text outfile.mp4
-vf subtitles=infile.srt...
Why `null >= 0 && null
...ncrements the value of a variable by 1 if its type is number and assigns 0 to the variable if not, where the variable is initially null or undefined .
...
Using async/await for multiple tasks
... |
edited Jul 7 '16 at 10:41
answered Sep 9 '12 at 11:35
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What is a good regular expression to match a URL? [duplicate]
...you want to ensure URL starts with HTTP/HTTPS:
https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)
If you do not require HTTP protocol:
[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)
To try this out s...
Fitting empirical distribution to theoretical ones with Scipy (Python)?
INTRODUCTION : I have a list of more than 30,000 integer values ranging from 0 to 47, inclusive, e.g. [0,0,0,0,..,1,1,1,1,...,2,2,2,2,...,47,47,47,...] sampled from some continuous distribution. The values in the list are not necessarily in order, but order doesn't matter for this problem.
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What is the fastest integer division supporting division by zero no matter what the result is?
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107
Inspired by some of the comments I got rid of the branch on my Pentium and gcc compiler using
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