r_code

Conditional Statements

参考 Schouwenaars (2016)

else if 学习

num_views <- 14

if (num_views > 15) {
  print("You're popular!")
} else if (num_views <= 15 & num_views > 10) {
  print("Your number of views is average")
} else {
  print("Try to be more visible!")
}

## [1] "Your number of views is average"

Because R abandons the control flow as soon as it finds a condition that is met, you can simplify the condition for the else if part in the second construct to num_views > 10. DataCamp

注意这个地方num_views <= 15是多余的。

另外这里的 if else 条件不是向量化的，因此需要对向量执行时，需要加 map 函数

num_views <- 10:20

if (num_views > 15) {
  print("You're popular!")
} else if (num_views <= 15 & num_views > 10) {
  print("Your number of views is average")
} else {
  print("Try to be more visible!")
}

## Warning in if (num_views > 15) {: 条件的长度大于一，因此只能用其第一元素

## Warning in if (num_views <= 15 & num_views > 10) {: 条件的长度大于一，因此
## 只能用其第一元素

## [1] "Try to be more visible!"

suppressMessages(library(tidyverse))
map(num_views,
    ~if (. > 15) {
  print("You're popular!")
} else if (. <= 15 & . > 10) {
  print("Your number of views is average")
} else {
  print("Try to be more visible!")
}
)

## [1] "Try to be more visible!"
## [1] "Your number of views is average"
## [1] "Your number of views is average"
## [1] "Your number of views is average"
## [1] "Your number of views is average"
## [1] "Your number of views is average"
## [1] "You're popular!"
## [1] "You're popular!"
## [1] "You're popular!"
## [1] "You're popular!"
## [1] "You're popular!"

## [[1]]
## [1] "Try to be more visible!"
## 
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## [1] "Your number of views is average"
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## [1] "Your number of views is average"
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## [1] "Your number of views is average"
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## [[5]]
## [1] "Your number of views is average"
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## [[6]]
## [1] "Your number of views is average"
## 
## [[7]]
## [1] "You're popular!"
## 
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## [1] "You're popular!"
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## [[9]]
## [1] "You're popular!"
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## [[10]]
## [1] "You're popular!"
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## [1] "You're popular!"

在进行到这一步后，会考虑进行 loops 运算，如 for loops 或者 while loops，后续会介绍。

Schouwenaars, Filip. 2016. “Intermediate R.” 2016. <https://www.datacamp.com/courses/intermediate-r>.