R 在pdf输出的可缩放表格中创建水平线

我正在使用rmarkdown创建pdf文档，但无法获得每个块的水平线分隔。代码如下

---
title: "Some title"
author: Arvin
date: "October 18, 2016"
output: pdf_document
fig_caption: yes
---


```{r script1, echo = FALSE}
df1 <- data.frame(A1 = c("Sometext", "", "", "B1", "Sometext", ""), 
                  A2 =  c("a", "b", "c", "B2", "d", "e" ),
                  check.names = FALSE)
knitr::kable(df1, caption = "Summary Table")           
```

---
标题：“一些标题”
作者：阿文
日期：“2016年10月18日”
输出：pdf\U文件
图片说明：是的
---
```{r script1，echo=FALSE}
df1我建议使用R-package
xtable
，它在高级功能和表格样式方面非常强大。在你的情况下，我会写：

---
title: "Some title"
author: Arvin
date: "October 18, 2016"
output: pdf_document
fig_caption: yes
---


```{r script1, echo = FALSE, results='asis'}
df1 <- data.frame(A1 = c("Sometext", "", "", "B1", "Sometext", ""), 
                  A2 =  c("a", "b", "c", "B2", "d", "e" ),
                  check.names = FALSE)

print(xtable::xtable(df1), hline.after = c(-1,0,3,6), comment=F)
```

---
标题：“一些标题”
作者：阿文
日期：“2016年10月18日”
输出：pdf\U文件
图片说明：是的
---
```{r script1，echo=FALSE，results='asis'}
谢谢你的回复。是否可以从printNevermind中删除行名，
include.rownames=FALSE
获取所需的输出
---
title: "Some title"
author: Arvin
date: "October 18, 2016"
output: pdf_document
fig_caption: yes
---


```{r script1, echo = FALSE, results='asis'}
df1 <- data.frame(A1 = c("Sometext", "", "", "B1", "Sometext", ""), 
                  A2 =  c("a", "b", "c", "B2", "d", "e" ),
                  check.names = FALSE)

print(xtable::xtable(df1), hline.after = c(-1,0,3,6), comment=F)
```