70-R茶话会15-你的编程菜鸟路上缺失的一课

参考：

• Ten random useful things in R that you might not know about - KDnuggets[1]

前言

一个都是些非常有启发的建议。不谋而合的是，很多我之前都介绍过了。

这就是优秀者们的马太效应吗！

1-switch和case_when

在做数据分析时，常常遇到的一个场景是，1,2,3 需要转换成其对应的"a","b","c"。比如在对结果进行分类统计的时候。

这时候或许可以借助循环和switch 实现替换，教程在，[[17-R编程03-控制语句与函数]]：

> sapply(tmp, function(x){
+   switch(EXPR = x,
+          a = 1, 
+          b = 2, 
+          c = 3)
+ })
c b c c b c c c c a a a b b b b c b a a 
3 2 3 3 2 3 3 3 3 1 1 1 2 2 2 2 3 2 1 1 

但这样的循环编程语法是低效的，dplyr 提供了向量化的操作[[37-R茶话会07-高效的处理数据框的列]]：

> dplyr::case_when(
+   tmp %in% "a" ~ 1,
+   tmp %in% "b" ~ 2,
+   tmp %in% "c" ~ 3,
+   TRUE ~ 0
+ )
 [1] 3 2 3 3 2 3 3 3 3 1 1 1 2 2 2 2 3 2 1 1

2-R 的快捷键

我早就介绍过了：[[05-R工具指南04-俺的技巧与Rstudio的快捷键]]

3-通过设置系统变量保护脚本中的密码不外露

如果你的脚本中需要你的某些签名或密码，最好不要把他们放在脚本里，因为你的脚本可能会分享给其他人。

可以使用系统变量：

Sys.setenv(
  DSN = "database_name",
  UID = "User ID",
  PASS = "Password"
)

接着在脚本中使用这些键即可：

db <- DBI::dbConnect(
  drv = odbc::odbc(),
  dsn = Sys.getenv("DSN"),
  uid = Sys.getenv("UID"),
  pwd = Sys.getenv("PASS")
)

4-代码格式化问题

其实我已经介绍过[[41-R茶话会08-优秀的R使用者，优秀的代码习惯]]，以及包：[[22-R茶话会03-美化代码]]

这一次来看看tidyverse 官方的包：Welcome | The tidyverse style guide[2]

网站也提供了相关tidyverse 团队的代码书写习惯。

5-学会在你的R 分享内容里使用变量

以Rmd 为例子: You can do this by defining parameters in the YAML header of your R Markdown document, and giving each parameter a value.

params:
  animal_name:
    value: Dog
    choices:
      - Dog
      - Cat
      - Rabbit
  years_of_study:
    input: slider
    min: 2000
    max: 2019
    step: 1
    round: 1
    sep: ''
    value: [2010, 2017]

Now you can write these variables into the R code in your document as paramsanimal_name and paramsyears_of_study. However, if you knit with parameters by selecting this option in RStudio’s Knit dropdown (or by using knit_with_parameters()), a lovely menu option appears for you to select your parameters before you knit the document. Awesome!

6-用 revealjs将Rmd 结果输出为html 幻灯

参见一个例子：hr_meetup_london/presentation.Rmd at master · keithmcnulty/hr_meetup_london (github.com)[3]

以及官方教程：rstudio/revealjs: R Markdown Format for reveal.js Presentations (github.com)[4]

例子如下：revealjs/simple.Rmd at main · rstudio/revealjs (github.com)[5]

结果以html 显示，感觉很棒：

我现在给别人作项目，直接交Rmd，和html 的输出，可以用这个包将html输出转成类似ppt 的效果。

7-shiny 相关

flexdashboard快速搭建shiny分析网页

flexdashboard 包提供了一个快速搭建shiny分析网页的可能。

ps：似乎shiny 的拓展分析页面模板非常多，这里我持谨慎太多。例子：Example projects • flexdashboard (rstudio.com)[6]

shiny 测试的两个好用函数：req and validate functions

• The req() function allows you to prevent an action from occurring unless a another variable is present in the environment, but does so silently and without displaying an error. So you can make the display of UI elements conditional on previous actions.

output$go_button <- shiny::renderUI({

  # only display button if an animal input has been chosen

  shiny::req(input$animal)

  # display button
  
  shiny::actionButton("go",
                      paste("Conduct", input$animal, "analysis!")
  )
})

• validate() checks before rendering an output and enables you to return a tailored error message should a certain condition not be fulfilled, for example if the user uploaded the wrong file:

# get csv input file

inFile <- input$file1
data <- inFile$datapath

# render table only if it is dogs

shiny::renderTable({
  # check that it is the dog file, not cats or rabbits
  shiny::validate(
    need("Dog Name" %in% colnames(data)),
    "Dog Name column not found - did you load the right file?"
  )

  data
})

关于更多介绍，参考：In R Shiny, when is an error really an error? | by Keith McNulty | Towards Data Science[7]

8-没事夸夸自己，装装逼

学习这么久，不如让R 包praise 夸夸你把。

Restarting R session...


If you think you can learn all of R, you are wrong. For the foreseeable future
you will not even be able to keep up with the new additions.
   -- Patrick Burns (Inferno-ish R)
      CambR User Group Meeting, Cambridge (May 2012)

[1] "You are lovely!"
[1] "You are outstanding!"
Hello Peng!
Welcome at Mon Dec  6 11:47:48 2021
We will use 3 cores for installing.

比如添加到启动环境里，见面就夸我，怪不好意思的，[[10-R工具指南09-自定义R的启动环境]]

花里胡哨的tag

Most people don’t take full advantage of the HTML tags available in R Shiny. There are 110 tags which offer shortcuts to various HTML formatting and other commands. Recently I built a shiny app that took a long time to perform a task. Knowing that the user would likely multitask while waiting for it to complete, I used tags$audio to have the app play a victory fanfare to alert the user when the task was complete.

参考资料

[1]Ten random useful things in R that you might not know about - KDnuggets: https://www.kdnuggets.com/2019/06/ten-useful-things-r.html

[2]Welcome | The tidyverse style guide: https://style.tidyverse.org/index.html

[3]hr_meetup_london/presentation.Rmd at master · keithmcnulty/hr_meetup_london (github.com): https://github.com/keithmcnulty/hr_meetup_london/blob/master/presentation.Rmd

[4]rstudio/revealjs: R Markdown Format for reveal.js Presentations (github.com): https://github.com/rstudio/revealjs

[5]revealjs/simple.Rmd at main · rstudio/revealjs (github.com): https://github.com/rstudio/revealjs/blob/main/examples/simple.Rmd

[6]Example projects • flexdashboard (rstudio.com): https://pkgs.rstudio.com/flexdashboard/articles/examples.html

[7]In R Shiny, when is an error really an error? | by Keith McNulty | Towards Data Science: https://towardsdatascience.com/in-r-shiny-when-is-an-error-really-an-error-702205ebb5d5