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What's the fastest way to merge/join data.frames in R?
...he first. If there are duplicates in the second data frame then the match and merge approaches are not the same. Match is, of course, faster since it is not doing as much. In particular it never looks for duplicate keys. (continued after code)
DF1 = data.frame(a = c(1, 1, 2, 2), b = 1:4)
DF2 = da...
What's the difference between echo, print, and print_r in PHP?
I use echo and print_r much, and almost never use print .
11 Answers
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How to read the output from git diff?
The man page for git-diff is rather long, and explains many cases which don't seem to be necessary for a beginner. For example:
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Ukkonen's suffix tree algorithm in plain English
...st String Searching With Suffix Trees , but he glosses over various points and some aspects of the algorithm remain unclear.
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Are +0 and -0 the same?
Reading through the ECMAScript 5.1 specification , +0 and -0 are distinguished.
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Generating random whole numbers in JavaScript in a specific range?
How can I generate random whole numbers between two specified variables in JavaScript, e.g. x = 4 and y = 8 would output any of 4, 5, 6, 7, 8 ?
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What is the best way to compute trending topics or tags?
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This problem calls for a z-score or standard score, which will take into account the historical average, as other people have mention, but also the standard deviation of this historical data, making it more robust than just using the average.
In your case a z-sc...
How to use php serialize() and unserialize()
... means to put the structure into a "lower common denominator" that can be handled by things other than PHP, like databases, text files, sockets. The standard PHP function serialize is just a format to express such a thing, it serializes a data structure into a string representation that's unique to ...
Read an Excel file directly from a R script
... directly into R? Or should I first export the data to a text- or CSV file and import that file into R?
12 Answers
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Is there ever a time where using a database 1:1 relationship makes sense?
I was thinking the other day on normalization, and it occurred to me, I cannot think of a time where there should be a 1:1 relationship in a database.
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