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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 - ...
...C的基础
1.1. 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 typede...
How do I make a matrix from a list of vectors in R?
...ne option is to use do.call():
> do.call(rbind, a)
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 1 1 2 3 4 5
[2,] 2 1 2 3 4 5
[3,] 3 1 2 3 4 5
[4,] 4 1 2 3 4 5
[5,] 5 1 2 3 4 5
[6,] 6 1 2 3 ...
Summarizing multiple columns with dplyr? [duplicate]
...df %>% group_by(grp) %>% summarise_all(list(mean))
#> # A tibble: 3 x 5
#> grp a b c d
#> <int> <dbl> <dbl> <dbl> <dbl>
#> 1 1 3.08 2.98 2.98 2.91
#> 2 2 3.03 3.04 2.97 2.87
#> 3 3 2.85 2.95 2.95 3.06...
Linux下安装项目管理工具Redmine - 开源 & Github - 清泛网 - 专注C/C++及内核技术
...
# wget http://rubyforge.org/frs/download.php/60718/rubygems-1.3.5.tgz
# tar zxvf rubygems-1.3.5.tgz
# cd rubygems-1.3.5
# ruby setup.rb
3、Rake安装
# gem install rake //直接使用gem命令安装rake.
//也可以下载安装地址：http://rubyforge.org/...
Calculate difference in keys contained in two Python dictionaries
...
234
You can use set operations on the keys:
diff = set(dictb.keys()) - set(dicta.keys())
Here is...
Determine the data types of a data frame's columns
...o use ?str(). To explore some examples, let's make some data:
set.seed(3221) # this makes the example exactly reproducible
my.data <- data.frame(y=rnorm(5),
x1=c(1:5),
x2=c(TRUE, TRUE, FALSE, FALSE, FALSE),
X3=letters[1:5])
...
PHP Pass by reference in foreach [duplicate]
...ee');
foreach ($a as &$v) {
}
foreach ($a as $v) {
echo $v.'-'.$a[3].PHP_EOL;
}
As you can see, the last array item takes the current loop value: 'zero', 'one', 'two', and then it's just 'two'... : )
share
...
Regular expression that matches valid IPv6 addresses
...
30 Answers
30
Active
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Converting int to bytes in Python 3
I was trying to build this bytes object in Python 3:
13 Answers
13
...
“Cloning” row or column vectors
...
83
Here's an elegant, Pythonic way to do it:
>>> array([[1,2,3],]*3)
array([[1, 2, 3],
...