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What does -1 mean in numpy reshape?
...inal shape'
numpy allow us to give one of new shape parameter as -1 (eg: (2,-1) or (-1,3) but not (-1, -1)). It simply means that it is an unknown dimension and we want numpy to figure it out. And numpy will figure this by looking at the 'length of the array and remaining dimensions' and making su...
how to calculate binary search complexity
...rer as informal ones:
The question is, how many times can you divide N by 2 until you have 1? This is essentially saying, do a binary search (half the elements) until you found it. In a formula this would be this:
1 = N / 2x
multiply by 2x:
2x = N
now do the log2:
log2(2x) = l...
App Inventor 2 列表积木完全指南：从入门到精通，一篇搞定数据存储 - App...
...数据太多了，变量根本管不过来。 比如一个购物清单有 20 样商品，难道要建 20 个变量？一个用户通讯录有 100 条记录，难道要写 100 个变量？当然不用。列表（Lists） 就是帮你批量管理同类数据的利器。今天这篇文章，我会把 A...
App Inventor 2 列表的函数式编程 · App Inventor 2 中文网
...反馈
App Inventor 2 列表的函数式编程
第 1 部分：贝瑞的柠檬水摊
第1步：过滤
第2步：映射
第3步：缩减
第 2 部分：鲍勃同学的...
莱昂氏unix源代码分析 PDF - 文档下载 - 清泛网 - 专注C/C++及内核技术
...源代码交叉引用列表 9
第一部分 初始化、进程初始化 25
第二部分 陷入、中断、系统调用和
进程管理 75
第三部分 程序交换、基本输入/输出、
块设备 109
第四部分 文件和目录、文件系统、...
C#位运算符（C#按位与、按位或 等） - 更多技术 - 清泛网 - 专注C/C++及内核技术
...
1
~a
&
位逻辑与运算
2
a & b
|
位逻辑或运算
2
a | b
^
位逻辑异或运算
2
a ^ b
<<
位左移运算
2
a<<4
...
How do I convert an integer to binary in JavaScript?
...
526
function dec2bin(dec){
return (dec >>> 0).toString(2);
}
dec2bin(1); // 1
dec2...
Reshape three column data frame to matrix (“long” to “wide” format) [duplicate]
...o similar questions scattered around this site.
tmp <- data.frame(x=gl(2,3, labels=letters[24:25]),
y=gl(3,1,6, labels=letters[1:3]),
z=c(1,2,3,3,3,2))
Using the tidyverse:
The new cool new way to do this is with pivot_wider from tidyr 1.0.0. It returns a...
In Matplotlib, what does the argument mean in fig.add_subplot(111)?
... a single integer. For example, "111" means "1x1 grid, first subplot" and "234" means "2x3 grid, 4th subplot".
Alternative form for add_subplot(111) is add_subplot(1, 1, 1).
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Split delimited strings in a column and insert as new rows [duplicate]
...is another way of doing it..
df <- read.table(textConnection("1|a,b,c\n2|a,c\n3|b,d\n4|e,f"), header = F, sep = "|", stringsAsFactors = F)
df
## V1 V2
## 1 1 a,b,c
## 2 2 a,c
## 3 3 b,d
## 4 4 e,f
s <- strsplit(df$V2, split = ",")
data.frame(V1 = rep(df$V1, sapply(s, length))...