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Summarizing multiple columns with dplyr? [duplicate]
...u want to summarize only certain columns, use summarise_at or summarise_if functions.
Alternatively, the purrrlyr package provides the same functionality:
library(purrrlyr)
df %>% slice_rows("grp") %>% dmap(mean)
#> # A tibble: 3 x 5
#> grp a b c d
#> <int>...
C＋＋模板的特化 - C/C++ - 清泛网 - 专注C/C++及内核技术
...化<>整得那么彻底
首先推荐两个不错的网址：
http://www.cnblogs.com/cutepig/archive/2009/02/12/1389479.html
http://read.newbooks.com.cn/info/175115.html
先说类模板的特化吧：
谁都没的说的全特化：
// general version
template<class T>
class Compare
...
Is it possible to define more than one function per file in MATLAB, and access them from outside tha
...hen I was studying for my undergraduate degree in EE, MATLAB required each function to be defined in its own file, even if it was a one-liner.
...
SqlDataAdapter vs SqlDataReader
...
AdaTheDevAdaTheDev
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How do I create a parameterized SQL query? Why Should I?
...eUploader: {
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How to sign an android apk file
...cify what part you get stuck with after you work through it, I'd suggest:
https://developer.android.com/studio/publish/app-signing.html
Okay, a small overview without reference or eclipse around, so leave some space for errors, but it works like this
Open your project in eclipse
Press right-mous...
App Inventor 2 SQLite 拓展：超流行兼容主流SQL语法的迷你本地数据库引擎 ...
...展由中文网开发及维护，基于开源 aix-SQLite 拓展。
与 TaifunSQLite 功能类似，但TaifunSQLite是收费的，美刀。
.aix 拓展下载：
cn.fun123.SQLite.aix
SQLite
SQLite 是 Android 内置的小型、快速、独立的 SQL（结构化查询语...
Google Tag Manager 入门指南 - 更多技术 - 清泛网 - 专注C/C++及内核技术
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var s = document.getElementsByTagName(“script”)[0]; s.parentNode.insertBefore(ga, s);
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Trust Anchor not found for Android SSL Connection
...ke described in this post: Trusting all certificates using HttpClient over HTTPS
Although it is a bit more complex to establish a secure connection with a custom certificate, it will bring you the wanted ssl encryption security without the danger of man in the middle attack!
...