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R - Concatenate two dataframes?
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If you're getting the union of more than 2 data frames, you can use Reduce(rbind, list_of_data_frames) to mash them all together!
– Yourpalal
Aug 13 '15 at 21:12
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Database Structure for Tree Data Structure
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Have a look at Managing Hierarchical Data in MySQL. It discusses two approaches for storing and managing hierarchical (tree-like) data in a relational database.
The first approach is the adjacency list model, which is what you essentially describe: having a foreign key...
Why should I capitalize my SQL keywords? [duplicate]
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So does MySQL, and for good and for bad (mostly bad:-), many developers first exposure to SQL is through MySQL.
– Paul Tomblin
Mar 4 '09 at 13:41
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The command rbenv install is missing
...g the command:
git clone https://github.com/rbenv/ruby-build.git "$(rbenv root)"/plugins/ruby-build
On Mac OS X you can install it through homebrew:
brew install ruby-build
On Debian (version >= 7) and Ubuntu (version >= 12.10) both rbenv and ruby-build can be installed using apt-get (or...
Why doesn't Dictionary have AddRange?
...ddRange" by using IEnumerable extension methods:
var combined =
dict1.Union(dict2)
.GroupBy(kvp => kvp.Key)
.Select(grp => grp.First())
.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
The main trick when combining dictionaries is dealing with the duplicate...
How to use 'find' to search for files created on a specific date? [closed]
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You could do this:
find ./ -type f -ls |grep '10 Sep'
Example:
[root@pbx etc]# find /var/ -type f -ls | grep "Dec 24"
791235 4 -rw-r--r-- 1 root root 29 Dec 24 03:24 /var/lib/prelink/full
798227 288 -rw-r--r-- 1 root root 292323 Dec 24 23:53 /var/log/sa/sar...
John Carmack's Unusual Fast Inverse Square Root (Quake III)
... function in the Quake III source code which calculates the inverse square root of a float, 4x faster than regular (float)(1.0/sqrt(x)) , including a strange 0x5f3759df constant. See the code below. Can someone explain line by line what exactly is going on here and why this works so much faster t...
Can you configure log4net in code instead of using a config file?
...e;
roller.ActivateOptions();
hierarchy.Root.AddAppender(roller);
MemoryAppender memory = new MemoryAppender();
memory.ActivateOptions();
hierarchy.Root.AddAppender(memory);
hierarchy.Root.Level = Level.Info;
...
Using .gitignore to ignore everything but specific directories
...pository. You just don't.
#
# Solution: stick this file up your repository root (which it assumes is
# also the WordPress root directory) and add exceptions for any plugins,
# themes, and other directories that should be under version control.
#
# See the comments below for more info on how to add e...
Custom toast on Android: a simple example
...p://schemas.android.com/apk/res/android"
android:id="@+id/toast_layout_root"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dp"
android:background="#DAAA" >
<ImageView android:id="@+id/im...