Rmarkdown 乳胶输出：sapply 的问题答案

【问题标题】：Rmarkdown latex output: issue with sapplyRmarkdown 乳胶输出：sapply 的问题
【发布时间】：2020-07-09 16:20:37
【问题描述】：

请参阅下面的 reprex1 和 reprex2。 lapply 运行但 sapply 有一个 " 添加到 .tex 文件的第 87 行的开头，打破了它。

想法？

---
title: "reprex"
output:
  pdf_document:
    latex_engine: xelatex
editor_options: 
  chunk_output_type: console
---

{r reprex1, echo=FALSE, warning=FALSE, message=FALSE, results='asis'}

library(tidyverse)
library(kableExtra)

species = c("Human", "Droid")

lapply(species, function(x){
  
  starwars %>%
    select(name, birth_year) %>%
    kable() %>%
  kable_styling(fixed_thead = TRUE, latex_options = c("striped", "scale_down"))%>%
  row_spec(0, bold = TRUE)
})

{r reprex2, echo=FALSE, warning=FALSE, message=FALSE, results='asis'}

library(tidyverse)
library(kableExtra)

species = c("Human", "Droid")

sapply(species, function(x){
  
  starwars %>%
    select(name, birth_year) %>%
    kable() %>%
  kable_styling(fixed_thead = TRUE, latex_options = c("striped", "scale_down"))%>%
  row_spec(0, bold = TRUE)
})

【问题讨论】：

标签： r r-markdown kable

【解决方案1】：

首先，我认为您可能希望在函数中添加一行，该行实际上对变量 x 执行某些操作，例如过滤，否则您只会返回两次相同的输出。

sapply(x, f, simplify = FALSE, USE.NAMES = FALSE) 与lapply(x, f) 相同，因此您可以将下面sapply 语句的输出与simplify = TRUE 与simplify = FALSE 进行比较：

library(tidyverse)
library(kableExtra)

species = c("Human", "Droid")

str(sapply(species, function(x){
    starwars %>%
        dplyr::filter(species == x) %>%
        select(name, birth_year) %>%
        kable() %>%
        kable_styling(fixed_thead = TRUE, latex_options = c("striped", "scale_down")) %>%
        row_spec(0, bold = TRUE)
}, simplify = FALSE)[[1]])
#>  'kableExtra' chr "<table class=\"table\" style=\"margin-left: auto; margin-right: auto;\">\n <thead>\n  <tr>\n   <th style=\"text"| __truncated__
#>  - attr(*, "format")= chr "html"

str(sapply(species, function(x){
    starwars %>%
        dplyr::filter(species == x) %>%
        select(name, birth_year) %>%
        kable() %>%
        kable_styling(fixed_thead = TRUE, latex_options = c("striped", "scale_down")) %>%
        row_spec(0, bold = TRUE)
}, simplify = TRUE)[[1]])
#>  chr "<table class=\"table\" style=\"margin-left: auto; margin-right: auto;\">\n <thead>\n  <tr>\n   <th style=\"text"| __truncated__

^{由 reprex package (v0.3.0) 于 2020 年 7 月 9 日创建}lapply 返回一个列表（类为 c("kableExtra", "knitr_kable")，属性为 attr(*, "format")= chr "html")），而sapply 返回带有attr(*, "names")= chr "Human" 的字符向量。

【讨论】：