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How to sum a variable by group
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404
Using aggregate:
aggregate(x$Frequency, by=list(Category=x$Category), FUN=sum)
Category x
...
cartesian product in pandas
...port DataFrame, merge
df1 = DataFrame({'key':[1,1], 'col1':[1,2],'col2':[3,4]})
df2 = DataFrame({'key':[1,1], 'col3':[5,6]})
merge(df1, df2,on='key')[['col1', 'col2', 'col3']]
Output:
col1 col2 col3
0 1 3 5
1 1 3 6
2 2 4 5
3 2 4 6
See here f...
Why does auto a=1; compile in C?
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240
auto is an old C keyword that means "local scope". auto a is the same as auto int a, and becaus...
Replacement for “rename” in dplyr
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148
dplyr version 0.3 added a new rename() function that works just like plyr::rename().
df <- ...
How do I specify a password to 'psql' non-interactively?
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154
From the official documentation:
It is also convenient to have a ~/.pgpass file to avoid reg...
How do I fix “for loop initial declaration used outside C99 mode” GCC error?
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149
I'd try to declare i outside of the loop!
Good luck on solving 3n+1 :-)
Here's an example:
...
实战Nginx与PHP（FastCGI）的安装、配置与优化 - 更多技术 - 清泛网 - 专注...
...这里为了介绍PHP的FastCGI功能没有加入更多的编译选项。
4.配置与优化PHP-FPM
PHP的全局配置文件是php.ini，在上面的步骤中，已经将此文件复制到了/usr/local/php/lib/php.ini下。可以根据每个应用需求的不同，对php.ini进行相应的配置。...
高并发服务端分布式系统设计概要 - C/C++ - 清泛网 - 专注C/C++及内核技术
...次起不需要再向Global Master查询group信息（缓存机制）；（4）保持和Global Slave的强一致性同步，保持自身健康状态并向全局的“心跳”服务验证自身的状态。
现在我们结合图来逐条解释上述工作，显然，这个系统的完整轮廓已经...
Add one row to pandas DataFrame
...))
>>> df
lib qty1 qty2
0 name0 3 3
1 name1 2 4
2 name2 2 8
3 name3 2 1
4 name4 9 6
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