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Filter rows which contain a certain string
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Assign multiple columns using := in data.table, by group
...b col1 col2
# 1: 1 1 hi hello
# 2: 2 2 hi hello
# 3: 3 3 hi hello
# 4: 1 4 hi hello
# 5: 2 5 hi hello
# 6: 3 6 hi hello
x[ , c("mean", "sum") := list(mean(b), sum(b)), by = a][]
# a b col1 col2 mean sum
# 1: 1 1 hi hello 2.5 5
# 2: 2 2 hi hello 3.5 7
# 3: 3 3 hi hello ...
Determine the data types of a data frame's columns
...st few values of each variable):
str(my.data)
'data.frame': 5 obs. of 4 variables:
$ y : num 1.03 1.599 -0.818 0.872 -2.682
$ x1: int 1 2 3 4 5
$ x2: logi TRUE TRUE FALSE FALSE FALSE
$ X3: Factor w/ 5 levels "a","b","c","d",..: 1 2 3 4 5
@Gavin Simpson's approach is also streamlined, but p...
Split a vector into chunks in R
...(), split() and ceiling():
> d <- rpois(73,5)
> d
[1] 3 1 11 4 1 2 3 2 4 10 10 2 7 4 6 6 2 1 1 2 3 8 3 10 7 4
[27] 3 4 4 1 1 7 2 4 6 0 5 7 4 6 8 4 7 12 4 6 8 4 2 7 6 5
[53] 4 5 4 5 5 8 7 7 7 6 2 4 3 3 8 11 6 6 1 8 4
> m...
Applying a function to every row of a table using dplyr?
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answered Jul 14 '14 at 0:20
alexwhanalexwhan
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Objective-C 2.0 Mac和iOS开发实践指南 PDF扫描版 - 文档下载 - 清泛网 - ...
...1. C程序的结构
1.1.1. main函数
1.1.2 格式化
1.1.3 注释
1.1.4 变量和函数名
1.1.5 命名惯例
1.1.6 文件
1.2 变量
1.2.1. 整数类型
1.2.2 浮点类型
1.2.3 真值
1.2.4 初始化
1.2.5 指针
1.2.6 数组
1.2.7 字符串
1.2.8 结构
1.2.9 typedef
1.2.10 枚...
Maximum number of characters using keystrokes A, Ctrl+A, Ctrl+C and Ctrl+V
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CGRidCtrl控件 学习心得 - C/C++ - 清泛网 - 专注C/C++及内核技术
...能介绍... 1
2.2 框架介绍... 2
2.3 主要类介绍... 4
2.3.1 CGridCtrl类... 4
2.3.2 CGridCellCheck类... 5
2.3.3 CGridCellCombo类... 7
2.4 控件类CGridCtrl常用函数说明... 10
2.4.1 行和列的设置... 10
2.4.2 单元格信息设置.....
What are the differences between json and simplejson Python modules?
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json is simplejson, added to the stdlib. But since json was added in 2.6, simplejson has the adv...
“ValueError: zero length field name in format” error in Python 3.0,3.1,3.2
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answered Mar 27 '11 at 4:01
Winston EwertWinston Ewert
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