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How to randomize (or permute) a dataframe rowwise and columnwise?
...,]
> df2
a b c
3 0 1 0
4 0 0 0
2 1 0 0
1 1 1 0
By default sample() randomly reorders the elements passed as the first argument. This means that the default size is the size of the passed array. Passing parameter replace=FALSE (the default) to sample(...) ensures that sampling is done withou...
Secure hash and salt for PHP passwords
...nswer was written in 2008.
Since then, PHP has given us password_hash and password_verify and, since their introduction, they are the recommended password hashing & checking method.
The theory of the answer is still a good read though.
TL;DR
Don'ts
Don't limit what characters user...
How to determine if binary tree is balanced?
... move to do some actual programming now. I'm working on binary trees now, and I was wondering what would be the best way to determine if the tree is height-balanced.
...
What is the difference between & and && in Java?
...& operator in Java is used for verifying whether both its boolean operands are true , and the & operator is used to do Bit-wise operations on two integer types.
...
Options, Settings, Properties, Configuration, Preferences — when and why?
...In truth it doesn't really matter so long as your expected audience understands what you mean.
The biggest difference is between Properties, which usually affect a component or object, and the others, which affect the whole application.
Following an approximate lead from Visual Studio and other M...
What is the difference between gravity and layout_gravity in Android?
I know we can set the following values to the android:gravity and android:layout_gravity properties:
20 Answers
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Storing money in a decimal column - what precision and scale?
I'm using a decimal column to store money values on a database, and today I was wondering what precision and scale to use.
...
MongoDB relationships: embed or reference?
...n a single document as you can. Because MongoDB documents have structure, and because you can efficiently query within that structure (this means that you can take the part of the document that you need, so document size shouldn't worry you much) there is no immediate need to normalize data like yo...
Find duplicate lines in a file and count how many time each line was duplicated?
...at should do the trick in O(n) * avg_line_len. Does anyone know such a commandline tool?
– Droggl
Nov 20 '13 at 17:27
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Solving a “communications link failure” with JDBC and MySQL [duplicate]
... in different web sites, but non of them worked. Finally I changed my code and found out what was the problem. I'll try to tell you about different approaches and sum them up here.
While I was seeking the internet to find the solution for this error, I figured out that there are many solutions that...