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Select multiple columns in data.table by their numeric indices
...llowing all just work:
library(data.table)
dt <- data.table(a = 1, b = 2, c = 3)
# select single column by index
dt[, 2]
# b
# 1: 2
# select multiple columns by index
dt[, 2:3]
# b c
# 1: 2 3
# select single column by name
dt[, "a"]
# a
# 1: 1
# select multiple columns by name
dt[, ...
Replacement for “rename” in dplyr
...
Richard
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answered Oct 1 '14 at 16:35
aaronwolenaaronw...
How to install 2 Anacondas (Python 2 and 3) on Mac OS
...m wondering how to install properly second Anaconda (for work) with Python 2?
3 Answers
...
while (1) vs. while(True) — Why is there a difference (in python 2 bytecode)?
...e): pass and while(1): pass , but this is actually not the case in python2.7.
3 Answers
...
Nokogiri installation fails -libxml2 is missing
...
First, install the dependencies:
sudo apt-get install libxslt-dev libxml2-dev
If you still receive the error, you may be missing a compiler toolchain:
sudo apt-get install build-essential
You'll get the "libxml2 is missing" error if you're missing a build toolchain (at least I ran into this ...
How to validate date with format “mm/dd/yyyy” in JavaScript?
...sValidDate(dateString)
{
// First check for the pattern
if(!/^\d{1,2}\/\d{1,2}\/\d{4}$/.test(dateString))
return false;
// Parse the date parts to integers
var parts = dateString.split("/");
var day = parseInt(parts[1], 10);
var month = parseInt(parts[0], 10);
va...
Creating range in JavaScript - strange syntax
...
264
+1000
Under...
App Inventor 2 中的“2”是什么意思？ - App Inventor 2 中文网 - 清泛IT...
2010年12月App Inventor对外公测，此版本也称为App Inventor 1 或 App Inventor Classic，简称AI1。
2013年12月App Inventor 2发布，简称AI2。
AI两个版本的区别：
1、功能区别：AI1官方不再开发更新，因此功能及新组件没有AI2多。
2、代码编辑...
App Inventor 2 连接调试器的几种方式的比较 - App Inventor 2 中文网 - 清...
...扫二维码测试；否则使用最新版的AIStarter模拟器也可以。2、对于没有安卓手机的或需要一屏展示效果的，建议第二种：使用商业模拟器，速度快，模拟的场景也较AIStarter模拟器多一些。3、对于学生教学场景，功能测试要求不高...
App Inventor 2在不同的屏幕之间传值 · App Inventor 2 中文网
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