glue包介绍
glue包可用于自定义变量，然后通过传参的方式，对字符串部分内容进行自适应修改。
例如：可将日期赋值为：date = as.Date("2019-12-05")，然后通过字符串拼接的形式，实现文件名称自动更新，glue("The day is {date}."。
具体用法
## glue包
## 功能：用于将变量传入字符串并解释变量
## 安装
install.packages("glue")
devtools::install_github("tidyverse/glue")
## 使用
library(glue)
name <- "Hider"
glue('My name is {name}.') ## My name is Hider.
## 多行长字符串也可以连接在一块
name <- "Hider"
age <- 28
anniversary <- as.Date("1992-12-12")
glue('My name is {name},',
' my age next year is {age + 1},',
' my anniversary is {format(anniversary, "%A, %B %d, %Y")}.')
## My name is Hider, my age next year is 29, my anniversary is 星期六, 十二月 12, 1992.
## 可以把参数变量放到内部
glue('My name is {name},',
' my age next year is {age + 1},',
' my anniversary is {format(anniversary, "%A, %B %d, %Y")}.',
name = "Hider",
age = 28,
anniversary = as.Date("1992-12-12"))
## My name is Hider, my age next year is 29, my anniversary is 星期六, 十二月 12, 1992.
library(tidyverse)
`%>%` <- magrittr::`%>%`
head(mtcars) %>% glue_data("{rownames(.)} has {hp} hp.")
# Mazda RX4 has 110 hp.
# Mazda RX4 Wag has 110 hp.
# Datsun 710 has 93 hp.
# Hornet 4 Drive has 110 hp.
# Hornet Sportabout has 175 hp.
# Valiant has 105 hp.
library(dplyr)
head(iris) %>%
mutate(description = glue("This {Species} has a petal length of {Petal.Length}"))
# Sepal.Length Sepal.Width Petal.Length Petal.Width Species description
# 1 5.1 3.5 1.4 0.2 setosa This setosa has a petal length of 1.4
# 2 4.9 3.0 1.4 0.2 setosa This setosa has a petal length of 1.4
# 3 4.7 3.2 1.3 0.2 setosa This setosa has a petal length of 1.3
# 4 4.6 3.1 1.5 0.2 setosa This setosa has a petal length of 1.5
# 5 5.0 3.6 1.4 0.2 setosa This setosa has a petal length of 1.4
# 6 5.4 3.9 1.7 0.4 setosa This setosa has a petal length of 1.7
## 前前后后的空行、空格会自动忽略
glue("
A Formatted string
Can have multiple lines
with addititonal indention preserved.
")
# A Formatted string
# Can have multiple lines
# with addititonal indention preserved.
glue("
leading or trailing newlines can be added explicitly
")
# leading or trailing newlines can be added explicitly
## 使用\ 不换行
glue("
A formatted string \
can also be on a \
single line.
")
# A formatted string can also be on a single line.
## 双重大括号将不解释变量
name <- "Hider"
glue("My name is {name}, not {{name}}.")
# My name is Hider, not {name}.
## 可以使用.open和.close指定替代分隔符
one <- "1"
glue("The value of $e^{2\pi i}$ is $<<one>>$.",
.open = "<<",
.close = ">>")
# The value of $e^{2pi i}$ is $1$.
# 有效的代码都可以使用 双反斜杠
`foo}\`` <- "foo"
glue("{
{
'}\'' # { and } in comments, single quotes
"}\"" # or double quotes are ignored
`foo}\`` # as are { in backticks
}
}")
# foo
# 真心看不懂。。
## glue_sql()构建SQL脚本
con <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
colnames(iris) <- gsub("[.]", "_", tolower(colnames(iris)))
DBI::dbWriteTable(con, "iris", iris)
# 这部分待数据库配置好 再测试
## +号
y <- 1
y <- 5
glue("x + y") + " = {x + y}"
# x + y = 6
# x + y = 7
# x + y = 8
# x + y = 9
# x + y = 10
# 搞不懂 为什么会计算5次？
参考链接：tidyverse/glue